Urm what the hell?

I had Ubuntu installed after a messup with Linpus Linux but Ubuntu took up alot of memory I didnt have to spare with this SSD, so back on topic when I had Ubuntu installed I upgraded my ram to 1.5 but recently I installed XP and its working lovely just a bit slow like 6 second delays. But when I went into system it says I have 500mb of ram, same in dxdiag and on canyourunit.com. I have put a 512 in for now but can someone explain or help me why it worked but now doesnt? I havent updated my bios as far as I know and i installed drivers and updates after it said 500mb, but I also checked after the updates and it was the same.

 

First check if RAM is compatible with AA1 - if it is and system does not seen extra RAM, check if you installed this right and stick is inserted right way. Obviously there is another option - if RAM is compatible and inserted right it may be faulty...

 

It isnt on the list but it was working when I had Ubuntu, the ram works on my big Fujitsu laptop so it isnt faulty. And it was properly inserted I pushed until it clicked in.

 

Try again, if it fails it may be incompatible w/ the One.

What speed is it? 667MHZ?
533 Is recommended. (Although I use 667)

BTW: Did it work before?