Will this card work in my Windows XP system?

Yes it works with both XP & Vista. Its a couple generations old now but is still a very powerfull video card. This card is a DIRECTX 9 card so although it works with Vista it cant use it to its full advantage as you need a DIRECTX 10 card for all the bells & wissels. It does however support SHADERMODEL 3.0 so plays all the newer games like Crysis & Call of duty 4 just fine. ATI does make a HD 2600XT for AGP as well as a HD 3850 I believe. High end AGP slot cards are hard to come by & a bit more expensive than their PCI-E counterparts. They had a X1950XT AGP at 1 time but I think its been discontinued.