how to format C: HELP!

Is there software out there that i can format C:\ I am running 8.1 downloaded it and installed.
try to revert to 8 it wont let me says invalid key.Need some help.
Thank you John
Answer #1
http://pcsupport.about.com/od/windows-8/fl/format-hard-drive-windows-8.htm
Answer #2
Thank U I am dumber than a box of rocks cant get it to extract to D drive dvd rom drive.
Thank yu
John
Answer #3
what was original os on the pC, win 8?
Answer #4
what was original os on the pC, win 8?
Doesn’t really matter, you can’t revert back to Win8 from 8.1 unless you created USB recovery.
@OP: Guide for clean installing windows 8 (involving solutions for any problem you might encounter):
pcsupport.about.com/od/windows-8/ss/windows-8-clean-install-part-1.htm
Personally I’d recommend to go for seven since you’ll be bothered with the procedure.