Where's my disk space going?

Misconceptions and Definitions

CHKDSK doesn't free up disk space; at least not intentionally. CHKDSK checks for errors on the disk and attempts to repair them. Sometimes that repair can result in more free space becoming available, but that's not the point. On a disk that has no errors running CHKDSK will not result in more free space becoming available; in fact it won't change anything at all.

Defragging doesn't free up disk space. I've had people ask why defragging the machine didn't free up space. That's not what defragging is about. Defragging simply rearranges the information on your hard disk for more efficient access. It doesn't create any free space.

Disk space is not memory. I keep hearing people confuse these terms and it's important - particularly when asking for help - that the terms you use accurately reflect what it is you're talking about. To over-simplify a little:

• Memory is the RAM (for Random Access Memory) where your programs and data reside when they are in use. When you turn your computer off your memory is erased. To free up memory you might just run fewer programs at the same time.

• Disk space is your hard drive where data is stored permanently or until you or a program explicitly erases it. To free up disk space you delete files.

Another good difference to note is size. My laptop, for example, has 8 gigabytes of memory, but 150 gigabytes of disk space. Disk space on a machine is almost always much greater than its memory.

Somehow no matter how much we have, disk space never seems enough. As we collect pictures and programs, and programs themselves collect data, more and more disk space is consumed unless files are deleted.

TreeSize

But what files are taking up all that space?

TreeSize Free is a free tool that will show you what's taking up all the space on your machine. (A paid version is available with additional features, but for what we're doing the free version will suffice.) For example, here's a display of one of my hard disks:

You can see by the length of the numbers, and the length of the accompanying yellow bar, that the top level folders containing the most data are listed first. In this case the C:\Users folder contains over 27 gigabytes of data. If we expand that by clicking on the triangle to the left of the item, we see this:

Now we can see that within C:\Users, it's the Public folder that has the most data.

If I expand a few more levels down, choosing the largest each time we find:

Whoops.

Here we can see that it's my guilty pleasure, World of Warcraft, that's taking up 22 gigabytes of space on this machine.

Now I know. If I want to free up a lot of space quickly, all I need to do is uninstall WoW. (FYI: not gonna happen .)

Your Machine

Now, as to what's eating up the disk space on your machine, there's no way for me to know. However, using a tool like TreeSize you should be able to relatively quickly see what's taking up all that space and take appropriate action.

(This is an update to an article originally published October 8, 2007.
The original referred to a tool named "SpaceMonger",
the free version of which is no longer maintained.)