HELP "very" undeletable files

while updating from 32bit to 64 bit vista i generated an extra windows install folder. it was created when an install to one of my drives failed.

these base folders cannot be deleted. ive gone in and changed the owner to myself and set full control to all that i could. ive even used the command prompt after closing explorer.exe and it still tells be access is denied when i try deleting. and i've tried McAfee's shredder.

the exception to this is that when i go to the individual files and set control it works and i can delete. but there are tens of thousands of files and i cant go to each and every one of them.

so with this can anyone tell me of another method to try or a software so that i dont have to format it?