1) Check that the Windows Sound Control's "Mute" isn't on, and that mixer volumes (Wave, Synth, Line, CD, etc.) are all set on high.

2) Try deleting Appx/Client cache files (Win2k: C:\Documents and Settings\{yourWindowsID}\.appx\cache\).

3) The "Toolkit.getDefaultToolkit().beep()"code may or may not be what your desktop expects as the default beep. It may be associated with another control. Go to Control Panel > Sounds and Multimedia > Sound Events. Is there a Sound Event named "Default Beep"?

If not, go to Microsoft Knowledge Base Article 300406 http://support.microsoft.com/default.aspx?scid=kb;en-us;300406 titled: "Default Sound Is Unavailable in the Sounds Tool in Control Panel", and follow its instructions.

If there is a "Default Beep" Sound Event, check to see if it has a .wav file associated with it and that the .wav file really exists. If there is not a .wav there, set one and see if that works. If one does exist, try setting a .wav association with the Windows program events that do not have a sound attached until you find the one that works.

4) Try re-installing the Appx/Client.
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              Toolkit.getDefaultToolkit().beep()

... to the Java VM (rather than fire off a .wav file). The Java VM forwards that request on via the Windows OS to the external speaker, but it's possible it's going thru the Client PC's BIOS => internal speaker to produce a beep. (We can't really tell, as this is internal to the Java VM.)

It's possible something you installed or uninstalled may have changed the sound associated with the event the Toolkit.getDefaultToolkit().beep() is sending.