XP recognizes only 2 gb

I'm new here so please bear with me. I've just built a new SLI computer. I put in 2 OCZ 2 gb sticks. The bios registers 4 gb but windows only see 2. I knew it wouldn't see all four but two seems pretty low. I have two 512 mb graphics cards so that accounts for 1 gb of memory not being accessible, but what would cause the other gb to be lost? Is there anything I can do to recover some of that last one?

 I'm pretty sure XP's limits are 2 GB letme check. You better off upgrade to 32 bit vista if you that extra ram.

BudJ:

I'm new here so please bear with me. I've just built a new SLI computer. I put in 2 OCZ 2 gb sticks. The bios registers 4 gb but windows only see 2. I knew it wouldn't see all four but two seems pretty low. I have two 512 mb graphics cards so that accounts for 1 gb of memory not being accessible, but what would cause the other gb to be lost? Is there anything I can do to recover some of that last one?

OK this is limited info becuase I,ve only seen this paticular setting once. I was working on a friends computer where he added a 1gb stick  to an existing 512.So he had 2 slots one with 512 and one with 1 g! When booting to windows he only showed the 512 but the bios showed both!I dont remember the setting in the bios but it did having a setting for the bios and the OP system to reconize the ram! Changed the setting rebooted and it reconized both ! Now this was a Dell PC but the setting was there and it did work. Its just an idea you might want to go through the settings and see if you get lucky!

 64 bit XP will see more, but other than that i wont see it. the only thing you can do is get a new OS that is 64bit