The space on my hard drive has been running really low (just a few hundred megabytes left), so I decided to uninstall a bunch of unused programs. I came across an old version of nVidia PhysX that I no longer needed since I have an ATI card, so I uninstalled it. The weird thing is that when I did, my free space jumped up a whole 8 gigabytes. Is there any good reason for this to happen? PhysX itself is fairly small.
It could be the page file or temp files left behind in the App data and local settings.
if you used disk cleanup that could be the reason as well.
if you disabled the System Restore and re enabled it, it might have given you that amount of space. also the disk cleanup deleted all those temporary files.
some times your system will be affected with virus, please check any virus is there?
+1 on the Disk Clean up... I use that all the time and it seems to help alot