i saw this and i will try it.

"Dual core processors: FS9 allegedly doesn�t take advantage of the second processor.
But here is a neat trick how to force FS9 make use of both processors on a dual-core
system: Start Flight Simulator, load your flight in windowed mode, then press
Ctrl+Alt+Del to open the Windows Task Manager. Click the "Performance Tab" and
observe that FS9 is only using one processor. Unless you have tons of other programs
running, the left window will show a heavy load, the right graph a very low load. Click on
"Processes" and look for "fs9.exe" (if you click on "Mem Usage" it should be the first or
last item). Right-click "fs9.exe" and select "Set Affinity". Remove the check mark from
one CPU. Close the window, then repeat the process and select both CPUs again. FS9 will
now spread the workload over 2 processors. You should notice
a marked difference in performance. If this does not work on your PC, contact Microsoft
Support for the optional "dual-core hot fix"."

http://flyawaysimulation.com/postt21628.html

Interesting find, TC... Will give this a go!

Yup, same here - my dual-core laptop is already using both cores averaging around 45-50% usage each, and the quad-core desktop is using all four at something less than 40% each.