Windows 7 doesn't detect all CPU cores?

[Arbethea]

Because Windows 7 has been running well on my computer, I have installed it on my next door neighbours computer so he can try it. He has a Q9550 processor and it works well in Vista with Task Manager showing 4 cores.

When we tried Windows 7 it only shows 2 cores, even though this is a quad core CPU (not dual core).

If the computer boots back into Vista it shows all 4 and it works fine, so I don't think it's a hardware problem. Updating the BIOS didn't change a thing either.

 

[Ian]

That's strange, did it do it from a clean install? Try running msconfig from the start menu (as an admin).

Then click boot > advanced options > then click Detect HAL and set the number of processors at 4.

Once you restart, that should do the trick

 

[Arbethea]

Thanks. Went round to my neighbours last week and tried this, and it worked straight away. Do you know why it needs to be set manually, I thought it should be able to work out of the box?