According to the MS document linked below, the OEM version is "married" to the motherboard. New motherboard = new version of XP required (if it's OEM). I just can't believe they didn't consider hardware failure. I suppose if you bought a professionally built computer, this is covered under warrenty (new MB = new OEM OS) but if you built it yourself you are SOL.
I'm wondering how long ago this licensing change was made. Was this last year?