Most PC users may burn a cd/dvd in the background , write word process, and browse or email at the same time. Why do i need two or more cpu's running at 3000 mhz to do this? Its because the hardware architecture and the OS are crap.
You don't need 2 or more cpus running at 3ghz to do this. As a matter of fact, I remember doing things like this quite effectively with a pentium 2 running around 300 mhz.