512mb stick of ram wont work

I have a 512 mb stick of ram that I have used before, and decided to install it again since I now have Windows XP and can use it. I normally ran with my stick of 256 mb Crucial ram with Windows 98, and that was sufficient for that OS. But now that I have XP, I was wanting to add the 512 to the 256 to speed things up, except that the 512 wont work right when put in. I tried it in the first slot, the second slot, and by itself in the first and second. The best that I could manage was to get it to be recognized with the 256, but it only recognized 128 of it (a total of 374). Like I said, I have used this stick before, and it worked fine, its just that windows 98 didnt like 784 megs of ram so I took out the 512 and ran on the better Crucial 256 ram. What could be the problem? Could the stick of ram have gone bad? I kept it in the anti-static bag that it came in, and didnt abuse it either. The ram is Nuetron brand.

OK, so was it just that I posted a stupid question? Or is it just that nobody has a clue as to why I cant get the ram working?

try installing the 512 MB stick of RAM alone, and running the computer at Default speeds. I've had a problem before where RAM would run at higher FSBs, but would not recognize the entire amount of RAM. Let me know if it recognizes the entire 512 MB at default speeds.

I will try it again at defaults. I had already dropped it down to just "fast" speed, but it still didnt work right. I will try dropping it down to normal, cas3 and see if it will work then. The problem is that Windows XP wont boot with that stick in when it doesnt recognize the whole thing lol. Guess that you cant fool it like you could with Windows 98. Ill report back with my findings.

OK dude. You were right, it wasnt the settings of the ram speed itself, like I tried before, but my OC. That pos stick of ram wont run at 133 fsb speed. I did get it to work though at 100 fsb, but now my overall system runs slower lol. Looks like I will have to try and trade this stick of 512 to someone for a 256 or even a good 128 mb stick of PC133 ram.

glad I could help.