Originally Posted by skalogre
Nope, should be fine as long as the activation code that came with the eMachine is used. AFAIK M$ uses the same code structure for full and repair versions.
No, they use different codes for OEM versions and retail versions, and IIRC the OEM versions are coded to the processor serial numbers, etc. However, if you install someone else's copy (assuming they are not also using the serial number or this would be "illegal" or at least against the license agreement) you can still activate it on a different computer and it will install fine. If you have trouble activating it online, you call their number and their system will activate it for you. You may have to promise that it is only installed on one computer.
Personally, I think since you already paid for a copy of XP with the computer, you have rights to do whatever is necessary to get a copy of XP Home working on the computer without buying another copy. But MS probably doesn't see it that way.