Guys, my vista isn't showing two CPU's in task manager (CPU history only has the "One Graph Per CPU" option), however device manager does show I have two "Intel 4 3.2 CPU"s under processors.

When I run 'while(true) {}' through cscript.exe, the cscript.exe process goes to 100%, I would have thought with hyperthreading it would only go to 50% at most.

Looks like hyperthreading is almost working but not quite.

Can anyone with Vista and hyperthreading check/confirm with their system?

I know it doesnt help your situation but on my dual core machines Vista detects them 2 CPUs. I've done a quick google and it says Vista definetly supports HT, maybe a BIOS update might show better results?

I'm pretty sure that Vista has changed a few things about it's CPU usage so I'd expect your cscript to use 100% instead of the 50% like XP would, presumably because MS tweaked it a little and decided to show the overall CPU usage as opposed to per CPU usage (if that makes sense).

Fair enough, I'll try on another forum just to be sure- but I am about to give up. Thanks anyway