If you have the original CD then just stick it into your computer, restart your computer, and when you see something along the lines of "press [key] to enter bootmenu" press whatever key it says, and then setup your computer to boot from the CD drive. Restart your computer again after you save your settings, and the CD will boot. Then follow the directions from there.
You don't need to format your hard-drive and reinstall windows, you could just go through your computer and delete the hacks.