For gaming purpose na po to? Kasi last time pumutok yung video card kasi di na kayanan yung graphics eh. At compatible po ito sa Windows XP? Ask lang po ako 
you have to consider a couple of things before going up on a good video card
1. kelangan mo ng PSU or Power Supply na compatible sa wattage ng computer mo kung may stock na 300W ka kelangan mo palitan to into 500W or more depende sa V-card na kelangan mo
2. kelangan mo alamin kung ilang watts yung V-card na gusto mo example yung HD 7770 ng AMD nasa 450W min wattage supply ang kelangan mo plus pa po yung wattage ng Processor and other stuffs that you had on your rig
3. monitor na gagamitin mo
example if it's 1080p ilang inches kasi alam ko may problem ilang video card na sobrang taas ng resolution it may stress them out fast at maaring masira kagad (pero optional to kanya kanya nalang paniniwala to
)
4. Clearance sa Case and Mobo aka Motherboard may ibang card na dual slots it means may mga pyesa ka na maaring tamaan sa loob kung malaki ang Video card mo example nalang ASUS 7770 ulit Dual Slot yun maaring matakpan yung ibang slot sa mobo mo like kabitan ng internet (PCI-E slot) if your using wifi antena , isa pang example longer video cards (EVGA GeForce GTX690 4GB)
maaring tumama sa lalagyanan mo ng CD or Hard Drive
hope it helps
