now here isn't a direct comparision but you get the idea. I went from a laptop with the 3.06 p4 to a custom built 2.26 core 2.
Laptop:
3.06 p4 with HT
1gb ram
xp pro
avg full scan: 45-50minutes
encoding of 350mb video file: roughly 3 hours
custom:
2.26 Core 2 duo
2gb ram
Windows vista business
full avg scan: 15 minutes
encoding of 350mb video around 45 minutes
video encoding is a cpu intensive process so you get a rough idea of the difference in speed.