Ok guys, two things -

Firstly, a Hyperthreading CPU, while appearing to your system as 2 individual CPU's, is in fact a very funky way of making one CPU behave like two. What this means is basically the CPU time-cycles (grunt) is split equally between two virtual CPU's. Now Intel have made some really cool changes to the CPU that make the virtual CPU's run much faster than half the speed of the host CPU but a hyperthreading CPU will never rival the performance of a dual core or even SMP (multi-CPU) systems.

The second thing is that Windowx XP Pro will only utilize 2 CPU's, no more. Now, a virttual CPU 'qualifies' as a second CPU so effectively if you had a machine with 2 Hyperthreading CPU's in it you would not be able to make use of all 4 virtual CPU's in XP. I know that MS are addressing this so that virtual CPU's are not classed the same is physical CPU's. How far they are I don't know but the new code may well be included in Vista.

My 2c as usual.