I just went through that exact same thing for a friend, removed everything from the hardrive that I even thought would conflict, like video, sound, modem, etc. spent about three hours preparing the drive, scandisked it, defragged it, put it in the machine it still wouldn't work. Save yourself the hassle, backup the files to transfer to CD or whatever, and do a clean install, I quarantee you one way or another you will end up doing a clean install. One other option is to get yourself a new hardrive, do the clean install on it, then install your old drive as a slave and transfer the files you need to transfer, to the new drive.