Heres a trick I discovered by accident:
Step 1: Select AVI file, Choose menus, Hit "burn"
Step 2: Open task manager right away and find DVDMaker.exe in the process window
Step 3: As soon as encoding hits 0.3 percent set the priority to high
If encoding jumps to 2.5 percent or higher shortly after then the trick is working, I tested this on Core 2 and Core quad with great results.
Mike