Strange problem with sound.....

Compaq 5423US, WinXP Home SP2, on board SoundMAX audio. Here's the deal: The little speaker down by the clock isn't doing its job 100%. It allows me to change the volume, but it won't play a sound. If I go to Control Panel > Sound and Audio Devices and try to use the horizontal slider, it also controls volume, but no sounds. If I click on the sounds tab, all the sounds actually play, and all the system sounds work (like on startup and shut down) but I can't get a sample of the loudness from the volume controls. I have to adjust the slider(s), then go to the Sounds tab and choose a sound (like Asterisk) and click the Play button (the little sideways triangle) to test the volume. Any ideas anyone? This one has me a bit lost..... any help will be appreciated!
THANX!

hd2k