Snow - an example. I am running SETI 24/7 (the Berkley Uni distributed computing analysis of Satelite data - searching for possible meaningful signals from space). My AMD2500+ system cracks more SETI code per hour than the AMD64. Both systems run Windows XP. (The AMD64 is dual boot to Mandrake 10). The 2500+ has 512meg RAM and the 64 has 1 gig. (both tweeked with msconfig ConservativeSwapfileuseage = 1). Check the NET - 32 bit apps on a 32bit OS will run slower on a 64 bit hardware.