Windows: If you routinely use Hibernation mode, this trick isn't for you. If you never use Hibernate mode on your desktop or laptop, this trick will free up 4-6GB of disk space on your system disk.
Over at the computer how-to site How-To Geek they've put together a guide to deleting your hiberfil.sys file and disabling hibernation mode. Some background, on the hibersys.fil:
So What is hiberfil.sys Anyway?
Windows has two power management modes that you can choose from: one is Sleep Mode, which keeps the PC running in a low power state so you can almost instantly get back to what you were working on. The other is Hibernate mode, which completely writes the memory out to the hard drive, and then powers the PC down entirely, so you can even take the battery out, put it back in, start back up, and be right back where you were.
Hibernate mode uses the hiberfil.sys file to store the current state (memory) of the PC, and since it's managed by Windows, you can't delete the file.
Check out the step-by-step walk through at the link below to disable Hibernate mode in Windows 7, Vista and XP and reclaim that chunk of disk space for better use. Have a tip or trick for freeing up space in Windows? Let's hear about it in the comments.
What is hiberfil.sys and How Do I Delete It? [How-To Geek]