I'm not certain of your question, but here goes:
If you need to reinstall Windows, I suggest DISABLING USB in BIOS and disconnecting any secondary harddrives. Then install Windows.
However, if you've already installed windows and your root drive letter is NOT C:, then try the following link:
http://support.microsoft.com/kb/223188
If it does not work (be advised it may be unbootable), try the first suggestion.