I've been trying to free up some hard disk space on my computer, so I downloaded WinDirStat (thanks Scott!).
I found a 1.5 GB file named "hiberfil.sys" and I had no idea what it was. A quick google search told me it was basically an un-needed file if you never put your computer in hibernate (which I never do), but it takes up space on your hard drive. It uses the same amount of space as your memory, so if you have 512 MB of memory, the file will be roughly 512 MB; if you have 1 GB, it will be 1 GB, etc...
If you want to free up some space, here's how to get rid of it:
Click Start, All Programs, Accessories, right click on “Command Prompt”, and then click “Run as Administrator”. If User Account Control (UAC) asks you for permission, permit the Command Prompt to run.
Next, type “powercfg -h off” (without the quotes), followed by pressing Enter.
Close the Command Prompt window and restart.
An alternative way of doing this:
Open Control Panel and select System and Maintenance.
Click on Power Options and click on Change plan settings for the plan that is selected.
Click on Change advanced power settings then click on the plus sign beside Sleep then the plus sign beside Hibernate after. Click on setting and change the counter to Never.
Open the Windows Control Panel
Double-click Power Options
Click the Hibernate tab, de-select the 'Enable hibernate support' check box, and then click Apply.
Restart your computer and hiberfil.sys will be automatically deleted.