Im having ALOT of trouble getting my computer to recognize a 256meg stick. I tried it in an older 400mhz amd and it recognizes right. Then when tried in Newwer 600mhz, only 128Megs. WHY?? My comp specs if it helps...
Windows XP Professional
System Model VIA Technologies, Inc. VT82C692BX
Processor
600 megahertz Intel Celeron
32 kilobyte primary memory cache
128 kilobyte secondary memory cache Board: 693-596-8671
Bus Clock: 66 megahertz
BIOS: Award Software International, Inc. 4.51 PG 06/02/00
Drives

256 Megabytes Installed Memory
128 Megabyte Module Size - 1 Installed
64 Megabyte Module Size - 2 Installed

Probably one of two things. Some motherboards/chipsets will only recognize single sided memory-RAM with chips only on one side-some will recognize double sided chips-RAM with chips on both sides of the card.

The other possibility is density. Some newer RAM is a higher density than the RAM that was standard when the motherboard was manufactured, and the board cannot recognize it.

I think this sounds like a single sided/double sided issue, from what I remember about past questions concerning density it usually will see about ¼ of the available RAM, while a board that only handles single sided will see half the amount available.