depends on if you have the 32 bit or x64 bit.
Right click on "My computer" and select "Properties" that should tell you what version you have.
If you have 32 bit then its 3.25gb i think...64 bit can handle way way more.
But your motherboard may also limit how much ram you can install too.
i dont have it installed but ill look at the cd
Goto start / run / winmsd.
that will tell ya what ya have. i have xp prp 32 bit
and says 4 gig. that is what i installed. i would not
install more than that. 3 gig will likely be fine for 32 bit.
64 bit ......almost no limit. dont have it.
i have windows xp pro is there a limit to how much ram it can use or have?
there are always limits to an OS just depends on what the specifics of that OS are