The Windows XP operating system also uses the SSE-2 instructions for non-temporal memory storage using the “movnti” instruction, for “Store Doubleword Using Non-Temporal Hint”.

Actually, IIRC, there is a setting you can enable before you power down to do your switch to 2 CPUs. When you power back up after the switch, XP should redetect your CPU and mobo setup.<P>I don't ...

Before building a dual-CPU machine, you'll need to calculate the cost of the motherboard, CPU, RAM, storage, and other components to see if it's viable for your requirements.

It seems a bit much given my systemspecs: Dual Athlon XP 1800, 1Gb Ram, Cheetah X15 18gb and 36LP 36Gb and an Adaptec 29160.

That's similar to the way Windows XP works today - if have a dual-CPU machine, you need to install XP Professional to use both CPUs. So what about dual-core CPUs? That's different.