Need more information. Could you send in the DXDIAG output?
I could guess, but that is all it would be. Maybe a dual core AMD system? If so, then right click on the Aces High II startup ICON, select "Properties", select "Compatibility", then set the game to run in Win98 mode. This worsk around a problem with XP and dual core AMD CPU's.
If that is not it, the I will wait to see the DXDIAG output.