I've had good luck just using a garden hose to blast out the crud from my computer. Works like a charm.
But no seriously, just use Dr. Delete if you need to delete a file or program and it's locked. Otherwise just go and reinstall windows, and when you do that selection the option to "delete partition" (make sure to delete the windows partition after you've backed up your data) then format and create partition then install windows.
Bam. Done.