You might have read the problems I was having with Half Life crashing on certain sound effects. I think I've sorted it out now, but I thought I'd post in case anyone was having similar problems.

I fiddled around with the audio options, testing it on an HEV power module. I found that if I maximised the "mp3" volume and reduced the HEV suit volume, I could pick up the power module without crashing, whereas it would always crash before. Seems it could be a Soundstorm specific bug.

Thanks to those who posted with tips. This seems like another reason to get an Audigy 2.