New
#11
It is actually new in Win7 where MS has made such an investment in getting the drivers into the installer and via optional Windows Updates that it often pays for building them itself under WHQL so it has them first, and manufacturers won't hold out.
So the recommended procedure is to do all of your Important and optional Windows Updates first after enabling Automatically get recommended drivers and updates for your hardware, and only then import any missing in Device Manager. You can then test performance to see if you need different drivers, and you will know if the issue is present with the baseline drivers Win7 wants.
There are exceptions with the GPU since Standard VGA is only meant to be a placeholder driver except for the oldest hardware.
I would pursue the Power Supply issue Layback brought up equally since it is a good possibility.