OK, I said 32 run faster because I have 2 computers running same app, VirtualDub, and the same movie, avi. One of them a P4 x86 2.8Ghz and the other an AMD x64 2800+ (1600Ghz) on the same case, I just replaced the MB. Memory, HDs, etc., are the same. P4 spent 45min.; AMD 30min. BTW, both running XP x86. It's a empiric test, but... I told about PLATFORM, not OS. Later, I run again the same app, on AMD x64. First with XP x86 and then with XP x64, no change noted, the same time CRAHAK you're right about OS, there's no gain, but with platforms there's a real gain.