Continous Restarts while upgarding to XP

Dear,

We are in process of upgrading XP prof. Presently our workstatoions are running in Windows NT and Win2k pro. We upgraded NT machines to Win2k and Win2k to XP. While doing this process, we are not able to complete this task. The System is restarting continuously in the middle of upgradation process (Configuring devices). So we reformating the system and then we are installing XP. Please help on this.

Thanks in Advance.
Kumar GH