We had an interesting experience trying to put Windows Server 2003 on a Dell PowerEdge 1900 the other day. I've run into this before, so once the other tech mentioned what was going on, I knew the steps to follow. Of course, this was after the install was failing due to some bad RAM mind you.

Well with functional RAM in the PowerEdge 1900, the install went mostly okay, except that you have to go into the BIOS and turn off the various extra bells and whistles of the Intel Xeon processor. I don't know if there's one or two specific things to be disabled, but I just turn off pretty much everything, like demand based power management, virtualization and so on. Once Server 2003 is installed, you have to update it to at least Service Pack 2.

After updating the PE1900 to Service Pack 2, you can go back in and turn on all the things that make a Xeon a nice processor. If you don't put SP2 on first, then when you try to boot back into Server 2003 the 1900 will continually reboot every time it gets to the Microsoft Windows logo screen. So put on SP2, set the Xeon back to normal, and you're golden.