Okay, I set up my Gateway GP6-450 with Windows XP to eventually network to my present desktop and I was messing around with it. I found out that it can support up to 768mb (contrary to what Gateway says, which is only 384) so I popped in the two 256 SDRAM sticks that I have, along with a 128 that was there, and it recognized it...then I had a thought, "I wonder what would happen if I replaced the 128 stick with a 512 stick..." so I did, I think the result speaks for itself:

(it says "Memory decreased in size" because I previously had 2 512 sticks in at which point it did nothing, so I took one out and replaced with the 256).
Unfortunately at this point Windows XP wouldn't load so I took out the 512 stick and replaced it with the 128 (total at this point=640), well Windows began to load then hit an error, and upon restarting I got the good ol' "NTFS.SYS not found" error, a brief minute in the recovery console fixed that, which happened because one of my 256 sticks turned out to be bad, so I replaced it with a 128 (total at this point=512). Windows loaded perfectly this time.
So...um, I don't suppose anybody has 2 spare 256 SDRAM sticks they'd be willing to part with if I pay shipping...? It's just a spare PC so I don't feel the need to buy them but if there's freebies available than why not....

My desktop with system properties open

This is my laboratory, also known as my bedroom. The gateway is the one on the floor and in the foreground is a dysfunctional (for now...) HP. My beloved desktop sits proudly on my printer stand