Are you overclocking the video card? What are the gpu temps during testing?
You dont need to re-install windows when adding 2gb or memory. No its not a OS limitation.
I'm not overclocking the GPU, it uses the bases values (Core 740Mhz and Memory 950Mhz).
The temperature ranges where I get artifacts in ATI Tools go from 52º till 61º that I think it's quite low for this kind of graphic card.
About the OS, what I mean that i didnt explain good, is that I'm using right now Vista32Bits so the RAM it's limited to 3GB so I'm losing the 1GB left, so I should install Vista64Bits to be able to use the whole 4GB modules of RAM. Just in the case it could be a problem.
Thank u for your fast answer