|Bogus ram, (sold as reg-ecc but not)|
Bad chipset support.
Not compatible ram.
Bios setting (most of the old servers had a limit to allow NT to be loaded) or battery bad.
Really any hardware issue such as loose pins or cold joint or ESD damage.
No matter how much you spent, you can get a much better system than trying to play with it too much.
Playing to the angels
Les Paul (1915-2009)