I am just curious as to what your objection with reformatting is? Especially if you are willing and planning on losing everything on the drive as it is.
If you are unwilling to format the drive, you could boot from a dos disk or something and go to each and every folder.
cd windows
del *.*
cd system32
del *.*
cd..
cd fonts
del *.*
cd drivers
de *.*
etc. etc.
A great way to spend the weekend. Just reformat ffs
edit: because I know somebody will eventually post this - yes, I know deltree could be used much quicker but i was making a point <g>