okay, I must inform you :
If you have an Nforce 2 soundstorm certified board and only if you have this (not all boards do) , then you have a DSP on board with a digital out. That's the one that provides hardware acceleration and is compatible with OpenAL 1.1, if you install it. It is a very high quality audio solution. However, because motherboard makers needed to cut costs, and the DSP did not have an analog codec by nvidia to change it's signal from digital to analog, the mobo makers packaged most boards with the now-discontinued, very cheap and poor quality Realtek ALC650 chip to provide the analog conversion on the motherboard. This is bad for 2 reasons : the ALC650 (an AC'97 codec) sucks, has no hardware acceleration (it's software based, which means it uses CPU time which is bad) and secondly, motherboards are very noisy, which detracts from the sound. If you install the ALC650 drivers, you may improve your sound, but you will completely lose the DSP ability of the nforce DSP (called the APU or MCP-T) which you should be aware of. This is only if you use the analog outs on the board. IF you use a digital out, you completely bypass the ALC650, use OpenAL 1.1 drivers and HW acceleration via the APU which is lower CPU than the AC'97, and a much cleaner and nicer sound.
In a nutshell, crappy AC97 codecs give the onboard sound a bad name. Try to use the digital out if you can. I do, and Freespace SCP sounds perfect. Make sure you have the MCP-T first tho. If you just have a MCP, you don't have soundstorm, and you should ignore this advice. (you'll have to, because you won't have a digital out)