Hi,
What kind of server are you refering to. Some server builders such as DELL have an option in the BIOS to limit the MEM to 256 MB. (OS INSTALL MODE) (And yes during P.O.S.T. it does show the the total mem installed although only 256 MB is used)
It has something to do with Windows NT having installation problems with systems with a lots of memory.
Hope this helps,
Herc.