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Reformatting erases everything on your disk. Recovering from an accidental reformat is unlikely unless you've prepared.

I formatted my computer and I lost all installed software. I don't have any of those to install again. What do I do?

For those of you shaking your head at this point, I need to tell you that this is a more common question and scenario than you might imagine. I'm sure you already know what I'm going to explain and suggest, so you probably don't need to read further.

This article is for the rest of you.

We need to understand exactly what formatting means, and what you need to do before you format to prevent the experience you, and others, just had.

If you remember nothing else, remember this:

Formatting erases everything on a hard disk.

If you've already formatted your machine, you've probably guessed that. Unfortunately, it appears that many people don't realize the total destruction that formatting implies.

"A format, by definition, returns a hard disk or other disk-like media to a blank and empty state."

A format, by definition, returns a hard disk or other disk-like media to a blank and empty state. All files, including operating system, applications, and user data are removed.

While the term "formatting" actually comes from a time when it meant something slightly different (the magnetic material on a hard disk actually had to be prepared or "formatted" before it could be used), today a format:

  1. Writes the information required by the operating system to to keep track of files that will eventually be written to the disk, aka the "file system". This step overwrites any such information that was there before, which means it erases everything.

  2. Writes data to the rest of the disk to set it all to a known state, and ensure that the rest of the disk is writeable. This step is actually optional, and since it can be time-consuming, when it's skipped you're doing what's called a "quick" format.

An unformatted disk doesn't have the basic information required to keep track of files you might want to put on it, so formatting is required. A disk doesn't really "lose" formatting, unless there's a failure of some sort, so reformatting is most often really just the fastest way to empty a disk completely. (Or change the type of filesystem, but I'm avoiding those details for purposes of this discussion.)

Formatting means: all data is erased. Remember that.

So, knowing (and remembering) that, how do you prepare?

Always get and save installation media. When you get a new machine, make sure to get Windows Installation (not repair) media, even if Windows is pre-installed. When you buy software, save the disks. Installation media are the only way you'll re-install key software if you're ever faced with an empty disk due to replacement or reformatting.

Save downloaded software. If you purchase software that's downloadable, always make sure to make a copy of what you've downloaded and save it somewhere else. I recommend burning to CD, for example. (Be sure and save any activation or license keys as well.) Even for free software that you wouldn't need to re-purchase, keeping the download handy can speed up the reinstallation process.

Backup your data. You should be doing this anyway, for any number of reasons. But the only way to get your data back onto your machine after a reformat is to have saved it somewhere else first. In other words, a backup.

Formatting, or rather reformatting, is often an appropriate first step to rebuilding a machine. It's important to know what it means so that you can be properly prepared to do so without any data loss.

What if it's too late?

What if you've already reformatted a machine, only to find out that doing so erased something important?

Stop using the machine.

I have to say that chances are extremely slim that you can recover, but if you use the hard disk at all for anything, then the chances just get worse and worse.

First, I will say that if you've done a "normal" or "unconditional" format (as opposed to a "quick" format), then you can probably pack it in right here. The entire hard disk partition will have been overwritten, and your data lost.

If, on the other hand, you've done the more common "quick" format, there's a sliver of hope. There are, in fact, "unformat" tools out there that claim to be able to recover data from an accidentally formatted disk. Like all deleted file recover tools, they rely on being able to analyze the data that's left on the disk. The problem is the more that you write to the disk - such as by installing Windows again - the more of that data is overwritten and the slimmer your chances of recovering anything.

I'll also say that this is something best left to people who have some expertise. It's easy while attempting to recover from an accidental format to make matters worse instead of better.

And, to be totally honest, my expectations are very low. If I were in your shoes, I'd probably resign myself to learning a hard lesson and move on.

Article C3665 - March 4, 2009 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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14 Comments
Velocity Wave
March 4, 2009 11:12 PM

For the more technically inclined, it is definately hard not to shake one's head at such a question as:

"I formatted my machine and now all my programs and data are gone, how do I get them back?"

That question is just one step away from:

"Hey Leo, I accidentally dropped coffee on my computer that contained valuable data. And then as luck would have it, I was conducting an experiment for class later that day, and pure hydrochloric acid spilled onto my computer. As if that were not enough, wouldn't you know it, but I hiking on a volcano a few hours later, when I tripped and fell. My already coffee stained, acide-damaged computer the rolled out of my backpack, and fell into a pool of lava, where it melted completely, and turned liquid-molten. Can I get my data back?"

Or:

"Hey Leo, I accidentally dropped my hard-drive into a distorted region of the space-time-continuum, known as a black-hole. I had some pretty important stuff on that hard-drive, like my pictures from last year's vacation. Anyways... I heard that information entering a black-hole is never really completely lost, and that over time, through hawking radiation, the black hole will "evaporate" and emit information about objects that have fallen within it. Do you know of a program that could analyze the hawking radiation and try to reassemble and unscramble my JPEGS?"

Jay Gieber
March 6, 2009 9:26 AM

Leo, a question for you. Let's say I partitioned my hard drive. (I do) Now let's say one partition becomes corrupted. (It did) Can I reformat just the corrupted partition and just replace those things that I had on it? Thanks, Jay

Yes. I glossed this over for simplicity, since most people run 1 partition on one disk. Formatting actually happens at the partition level.
- Leo
07-Mar-2009

BR Smith
March 10, 2009 9:50 AM

Leo, if "Formatting erases everything on a hard disk" then how could it be unformatted? I know many people mistakenly think if they format their drive someone else would not be able to retrieve that data, which is a terrible mistake.

Because most people do a "quick format" which essentially only erases the top level directory. Things can still be recovered from that. A full or unconditional format is more thorough.
- Leo
11-Mar-2009

Gigi
March 10, 2009 10:32 AM

Sorry to tell you Leo but you got it wrong: actually quick formatting doesn't erase the data just performs the process of setting up an empty file system on the disk, and installing a boot sector and the full formatting just adds scans to the disk at low level for broken sectors.
Imagine the hdd as a book: quick format just erases the content pages and the pages numbers, full format also checks for missing pages and tears or smudges on the page's paper.
Absolutely all the data is left untouched and this is why modern malware survives formatting.
Recovering data is dead easy - there are a lot of good freebies for it - and it's best done with the hdd in another pc.

Chris Robertson
March 10, 2009 10:39 AM

Fromatting only Destroys the FAT (index) but re-installing windows overwrites much of your data. I regularly recover a formatted drive (Files, not programs) using file Scavenger or undelete pro. Funny this is that computers that are fragmented do the best in recovery.

Alex Howe
March 10, 2009 11:51 AM

Easeus Data Recovery Wizard allowed me to recover over 400GB of music files I had on a second hard drive in my PC after I accidentally formatted it! (I got the drive letters transposed and thought I was formatting a new hd!!) As long as you DO NOT "write" any new data to the drive, it is possible!

jackson mccurdy
March 10, 2009 7:07 PM

I had to format and reinstall xp on my buddy's computer, after a motherboard replacement I ran some file recovery software and told his wife to go through it and pick out what she needs and she got back all her pictures,and could have got back a lot more stuff. She was so happy and she quit crying and everything. and said I was amazing. Now I'm pretty good with computers, but we are definitely not data recovery experts. And still got back a lot of data. So I don't know if telling them that there is not much hope for recovering their data is totally accurate. I suspect Windows gets reinstalled in roughly the same place on the hard drive as it was on the original install, leaving the rest of the data mostly intact. This was pretty easy to do just a little tedious.

Margaret Louk
March 10, 2009 8:18 PM

Hi: for those who are computer challenged, I suggest a card box. While I save a lot of things to my external hard drive, I have some downloaded programs. I make out a 3 x 5 card, put the name, date, purchase price (or free), web site, any numbers. I make sure I keep a copy of the key. When I reinstalled my operating system I was able to reinstall the games and other things I really wanted using this method. Easy. I had a problem with opening my old windows word programs, so I downloaded an open office program that opens them. Again easy. Sincerely Margaret

Vector
March 11, 2009 11:28 AM

Hi Leo. My operating system (Windows XP Pro is installed on partition C of my hard drive. If and when the time will come to reformat - can I reformat just this (c) partition, so that personal data on other partitions will not be lost? Thanks.

Yes.
- Leo
12-Mar-2009

pat harte
March 11, 2009 5:43 PM

HI . I HAVE A COMMENT TO ADD. I HAD AN 8GIG FLASH DRIVE THAT TURNED TO RAW AND WAS UNABLE TO READ ANTHING FROM IT AS WINDOWS DID NOT FIND IT
AFTER SEARCHING THE WEB FOR AN ANSWER I COULD NOT FIND ANY AND DECIDED TO FORMAT IT UNDER DISKMANAGMENT
AFTER I WAS ABLE TO RUN RECOVERY SOFTWARE AND RECOVER 96% OF ALL THE DATA.
WHAT IS THE BEST WAY TO RECOVER FROM A RAW DRIVE
MANY THANKS

Jack
March 16, 2009 10:09 AM

I also had formatted ( not quick format) my hard disk partition.

I recovered all the data ( 40 gb) using a software called GetData Back for NTFS

Hope it helps

maggie
July 25, 2009 8:14 AM

I bought a win vista lappy. I had no idea that reformatting would lose all my original programs installed when i bought the pc. Since xp put them back i thought vista would too...Is there a website to help me find a list of all programs originally installed on my PC when i bought it?

Not really. You need to get in touch with the manufacturer of that computer, since each will pre-load their machines with different collections of stuff.
- Leo
26-Jul-2009

y g
April 14, 2010 12:53 AM

is it possible to recover data from raw drives?

Mark Alter
September 6, 2010 12:18 AM

The recovery software are meant to recover the data saved on your hard disk partitions and these are not meant to re-install the softwares that were installed before formatting. To install the software again, you need the executable of the software you wish to install.
ALso, it is important to note here that, when you format your hard disk, you need to re-install the operating system. Similarly, you need to install each and every software again, after formatting.

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