Comment by mcb3k

You can actually use an unactivated copy of Windows 7 for longer by using "slmgr /rearm" in cmd (which needs to be run by right clicking cmd.exe and choosing the "run as administrator" option). You can extend the license 3 times (leading to 120 total days). It should be noted that you can apply it after the temporary licensing has expired.

I'm not sure if this applies to Windows 8 or 8.1, however.