I have a new comp with more then 3GB of ram so I switched from 32 to 64 but It now runs slower. With the 64bit I used Winrar to extract something and the comp is dead in the water until its done extracting. With the 32bit I could extract 4 things and watch a HD video and with the internet open w/7+ windows open some of wich were streaming Hd video as well. Also the boot time is alot longer with 64bit ver.
MOBO - Asus P5Q3 Deluxe
CPU - Core 2 Quad 2.83GHz @ 1333
RAM - Corsair 2GB DDR3 w/total of 8GB (4x2GB)
Video - Radeon HD4870 1GB Diamond ser.
Power - 1000Watt
That's the opposite of my experience. Assuming that you've installed all the correct 64-bit drivers for the motherboard and your peripherals, and are using 64-bit versions of the relevant software, I can't think of an explanation. In theory, and my experience backs this up, XP64 should be slightly faster than the 32-bit version.