No Validate after Re-install.....Help!

Hi There,

Ive recently built a PC fro scratch.

Ive installed my copy of windows xp professional, validated, updated, and all was ok until my Raid Disk started failing. I could not resolve the problem so i purchased new disks and setup a different raid. Ive installed windows with no problems and all is ok again, or so i thought.

However now i have come to update windows its saying my copy cannot be validated? So now i cant get the upgrades

Ive obviously used the same product key - its a genuine version of XP professional but its OEM not retail.

Would this make a difference?

Is it because the microsoft database has this copy as already registered?

Do i need to contact Microsoft?

Whats my next move?

Hope somone can help.

Alfony.