After upgrading to 8.1 you may notice that you have a rather HUGE file called "Windows.old" on your C: Drive. It's all your old Windows Files (hence the catchy name). You can't just delete it, but you can get rid of it using Disk Cleanup. Just enter "Disk Cleanup" in the Search Bar on the Start Page. Open the app and click "Clean System Files" at the bottom of the dialog box. Then select "Clean old Windows files..." Boom, just like that you've freed up 4.5 GB. ** Want another 2 GB free? Turn off Hibernation Mode using the method described here: 1) Open Command Prompt (as Administrator - right click) 2) Type powercfg -h off and hit enter. Done. That's a total of 6.5 GB free space Ur welcome. ** P.S., I did this and everything runs fine so I suppose it is safe. Of course, you break things it's on you.