I have a Fujitsu P2511 that powers down during Windows boot. The box will sit happily at the BIOS setup screen and at the Windows safe mode selection screen for extended periods but when Windows starts to boot it will drop the power. It is not entirely consisten when in the boot process it drops out, sometimmes it is very soon into the process other times it can get to the login screen and in some cases will run for an extended period with no problem.
It strated with WinXP but has persisted through an upgrade to Win7. I have replaced the PSU, memory, hard and DVD to no effect. I can't find any documented specific issue with this motherboard and wondered if anybody else has had a similar issue.