>Using VFP, if I upgrade to a dual core system, will the execution speed of my VFP apps slow down because VFP only uses one side of the dual core system?

Talking about a vfp app saturating the "remaining" cpu on a single core system:
If by weird chance the process thread is jumping the cores very often, there is a *theoretical* chance of slowdown, which in practice is more than evened by all other processes mostly running on the second core. BUT: You can force your application to run on specific core(s) only, minimizing such context switches while still reaping the benefits of background processing the other tasks.

HTH

thomas