Xp doesnt handle 4 gig memory, it can just have 3 gig at most, so you need to go with vista

, :ps: this is my new computer im getting
Xilence 420W 12cm Fan REDWING ATX12V V2.0
MSI 945P NEO5-F i945P 4DDR2-DIMM 3PCI 3PCIe SATA Audio GB-LAN Socket775 ATX
Intel Core 2 Duo E4500 2.2GHz 2MB FSB800 Boxed (with cpu-cooler!) Socket 775
Kingston 2x1024MB (tot. 2048MB) DDR2 PC6400/800MHz CL5
Hitachi Deskstar 0A31636 T7K250 250GB 7200rpm 8MB 8.5ms SATA2
Samsung 16X DVD-ROM BURNER /48X CD-ROM BLACK/SVART bulk IDE
Asus Extreme GeForce 8600GT SILENT 256MB DDR3 TV-out HDTV DUAL DVI RETAIL PCI Express