Reboot at Windows XP Login

I just installed a new motherboard. I am using an AMD Athlon 2000XP+. For some reason, I cannot have my FSB set for 133. If I do, at the Windows XP Pro login it restarts, if it makes it that far. It runs fine at 100 FSB though. I can also run it at 133 FSB in Linux Mandrake 9.2 without restarts. I’m thinking it could be my power supply. I’m using a 250 Watt.