I'm having memory problems, and not the kind you have when you get really old. Previously my computer had two sticks of 256 in it (there's only two slots) and I tried to upgrade one of those to a 512. Both the System dialog and DxDiag confirm that the memory is present, but for some reason it doesn't seem to use one of the sticks (looks like the 512, though sometimes it's the 256). I've tried swapping their positions with no luck. When I put in the 512 by itself with nothing else, it works fine. I really don't want to have spent $80 to upgrade my memory from 512 to 512. As for the specs, the RAM is PC2100, DDR, 266MHz, and CL 2.5. This exact same sticker is on both the 256s and the 512; the only difference is the listed capacity. Is there some kind of BIOS tweaking I need to do to get my computer to access the memory? Again, it acknowledges that it's there, but doesn't seem to be able to use it.

From what you have stated it sounds like the 2 sticks are not compatible. Do you know if one of them might be Ecc (error correction)? some MBs will use either one but not mixed. I would download AIDA32 and run it. It will tell you more info about that memory. Possibly that may help you sort it out.

Check your system board spec's. On some boards with DDR memory you have to add it in matched pairs.

I tried AIDA; looking at the SPD section there is only one thing different between the two sticks. The 512 has a "Reduced (7.8 us)" refresh rate and the 256 has a "Normal (15.625 us)" refresh rate (both are on Self-Refresh) and I doubt that would make much difference. All other specs are exactly the same between the two sticks, except of course the capacity. I wouldn't know about my motherboard's specs; AIDA says it's a FIC VC19, but when I follow the link it says nothing about adding RAM in matched pairs. Is there a certain keyword I should be looking for?

P.S. While AIDA claims my motherboard is a VC19, it's actually a slightly nonstandard VC37. Weird.

AIDA32 is simply reading the PnP identifier that is on every peice of hardware these days. If the board was modified and they didn't change the id tag on it then it will show up as the original. MSI uses multiple numbers for their MBs. Just another way to confuse us folks out here. FYI - Fic is considered by many to be a low quality board. The issues you are having may be because of that.