I have an old IBM Thinkpad T42 laptop. It was originally running WinXP Professional. I reinstalled the OS using a WinXp Home CD from another machine. I have it running at this point, but the OS wants to be registered. I have tried using the key on the label attached to the laptop, but it doesn't work. I assume that's because it's for the Professional version. Any suggestions on what to try next? If I buy a WinXP upgrade CD off of eBay, will that key work? Vanessa