Well, pretty much any system will boot from CD, so check your BIOS' boot settings.
If you dont have any windows disks lying around, then damn. Ill probably get in sh*t for this, but use a pirated one or something! If youre just wiping the disk, Ill bet MS wont even care...
Anywho, you can order free samples of ubuntu... itll take a while to get them to ya, but in general they're good for stuff like that. They also come with a "Live CD" meaning you run it off the CD and it boots into ubuntu, from which you can then erase your hard drive!
EVEN BETTER: Put in the ubuntu disk and go to install, wipe out the hard drive, format and partition it so it's ready to accept Windows, then just remove the disk and restart that beast.