Am I right in thinking that I could run 4Gb of ram in my system and vista will recognise it as 4GB etc but xp will still run fine but will only recognise about 3Gb of it? or will xp have problems? I need to keep the xp as the CAD/FEA software I have to use at uni isnt vista/64-bit compatible. But i Have some Spare 800mhz ddr2 around and thought I could use it.