QUOTE(Bourne @ Mar 10 2008, 18:45)

Hm... this thing used to happen to me. But in XP it won't just share the audio. If I am playing foobar2000, I can't use other audio-based programs like Skype for example (Error: Problem opening device...). I get the same error opening Winamp and then trying to play a song in Foobar2000.
The driver is listed as:
Creative AudioPCI (ES1370), SB PCI 64/128 (WDM)
Driver 5.1.2535.0
Bourne,
I'm using the exact same soundcard and drivers. Funny, I thought I was the only one still using such an archaic piece of hardware.
Could it be that you're using Kernel streaming in winamp and FB2K? If I turn on Kernel streaming in those programs I also get the "Problem opening device" error when I try to use multiple audio programs at once. Try using Directsound instead (in Winamp: Ctrl-P -> Plug-ins -> Output -> select "Nullsoft DirectSound Output", in FB2K: Ctrl-P -> Playback -> Output -> Select Output Device "DS: Creative Sound Blaster PCI" from the drop-down list.
Hope this helps, at least on my machine it works so your soundcard and drivers should not be the problem.