OFP player RALPH has confirmed that the following tweak applies to DirectX versions 8.0 and 8.1. However, if you previously performed the tweak for DirectX version 8.0 and have since upgraded to version 8.1, the tweak settings should be retained. If you're not sure or you want to check to be sure, go right ahead.
As supplied by Microsoft, DirectX versions 8.0 and 8.1 run a sound debugging program in the background under Windows. This debugging program may cause performance degradation and possibly execution errors in Windows applications using DirectX (such as OFP).
The DirectX sound debugging program can be safely disabled by downloading this DirectX applet and following these instructions:
This tweak has noticeably helped some while it appears useless to others. However, it's absolutely harmless, So it's worth giving it a try.
(With thanks to Brother Desloc and to Uncle Ahl, who notified the OFP player community about this).