Can I recover data after I accidentally formatted my hard disk?

You mentioned that you forgot to backup a crucial folder. The first lesson you should walk away from the experience with is simple: backup. And I don't just mean because you were about to reformat; I mean regular, periodic backups.

Let's face it: if your hard drive had died you also would have lost those crucial folders.

Hard drives do die, and regular backups can save your assets.

Second, in preparation for reformatting, you obviously did a backup where you pick and choose what files to copy off. As you've discovered, you can miss things. When performing a one-off backup for any reason, I once again recommend using a backup or imaging program to backup everything. Even if you never need 95% of it, that time when you need something in the 5% will make this step well worth it.

Now, as I said, a reformat by definition erases your hard disk. All of it, at once.

As it turns out, there are two common types of format: "normal" and "quick".

A "Quick" format simply erases the hard disk's root directory, twiddles a couple of other things, and you're done. Note that it did not actually go out and overwrite files.

A "normal" format actually goes out and overwrites all of the data on the disk. You'll know you're performing a normal format as it takes a long time.

If you've done a quick format, then there may be hope. You'll need to investigate "unformat" utilities or file recovery software. Normal "undelete" utilities will probably not work, as they often assume that you've simply deleted a file. Here you've deleted everything. A utility like GetDataBack might be called for. (There are others as well. This isn't something I've done a lot of, so perhaps readers will chime in with some utilities that have worked for them.) These utilities actually scan your entire hard drive and try to piece back together that which was erased. If not a lot has changed or otherwise been damaged, you can often get a lot of your data back.

This is why I say "stop using the drive". The more you use it, the more the contents of the drive changes, and the less likely it will be that your data can be recovered.

You'll notice I've focussed on "Quick" Format, and that's on purpose. It happens to be what most people do, which is fortunate, since data recovery from a complete format gets much trickier. In fact, in order to recover data from a true, data-overwriting normal format, you're typically talking data recovery services and a lot of money.