I know this is a long shot here, but it may be a windows service stopping you from using audio.
This has happened to me a few times when I killed one of the svchost.exe's in task manager.
To test, go into control panel and under classic view, (I just like it that way)
select the sounds and audio devices icon.
If it beeps when the error appears to tell you you have no sound drivers installed this will work.
click start > run
Type in services.msc
In the services list find windows audio, you may find it is disabled or stopped.
Start the service and try to play in winamp again.
OR
If the above does not work, does winamp still want your onboard sound card to use?
In winamp, push ctrl+p to open the preferences box.
on the left hand side there is the tree of items, near the bottom, select output.
you are using the direct sound DLL, this is good. select configure.
It may say primary sound driver, but change it to your new sound card and push OK then close preferences.
Try playing a song again.
The other alternative is of course the sound and audio box DOES open, and from there it is just a matter of sifting through the tabs and changing your new card to default.
