Back-up and System Restore

Hi,

Last night I decided to do a system back-up because I noticed that my
Windows firewall was turned off. I also thought that that doing the back-up
was a recommended process. I wanted to back up the files on CDs , but the
process began and I think my D drive just made a back up of itself on my
system because I went from having disk space to having 0% free. I went to
system restore and disk clean to reverse the back-up but it didn't work. I
just want to free up the space that was taken up by the back-up but I don't
know how to find where the files were backed up. Any help would be greatly
appreciated!
Thanks,
Burr