chances are the only thing you might need to do is bring it up, and reload the Nvidia Nforce driver set. You don't have to do a repair of Windows. Be smart and backup anything important before doing anything though. I took a harddrive that last ran on an Nforce3 AGP board, and ran it on an Nforce4 board. All I did was reload the Nvidia Driverset and it ran perfect.
Seconded - you should be able to re-boot the thing successfully without a repair or a reinstall. Just make sure you back up everything important first.