New hard drive- lenovo

Worst case, you just have to call Microsoft. Make sure you have your restore disks/partition or w/e the hell they give you nowadays. If not just torrent a lenovo OEM version of windows 7, this is perfectly legal as long as you're using your own activation number. I personally would take this opportunity to upgrade just find a nicer hard drive that uses the same slot/connection type and get something bigger/fancier!