I have a computer that came with Windows XP Home (with the sticker on it that has the product key). I used it for some time with a (legally obtained) copy of Windows. Now I want to reload the original Windows version and product key to give it to a relative. I can't give them my copy of Windows, since it came from my MSDN subscription and is only usable by me for software development/testing. When I load the machine from my Windows disk, it does not accept the product key on the sticker.
"The CD key you entered is not valid"
I did double check my keystrokes and the XP disk I am using had all versions and I did indeed choose the correct one (Home Edition) that matched the product key sticker.
EDIT: It is clear to me from the answers below that I am using a non-OEM disk with an OEM product key. I am the first one to understand Microsoft's need to protect their IP. However, it seems like there might be a way without tracking down and purchasing recovery disks for a five year old machine just to turn around and give the machine away.
Is there a way I can accomplish this?