Shoutbox

Check (all) your sound settings again though. This sounds exactly like you or some program set the properties of the sound scope to "Hall", "Church" or whatever...

First check the sound settings in Windows default config panel:
Configuration panel > Sounds > Volume > Speakersettings > Advanced

Also, there could be a program which further sets up the flavor of the sound. Normally this program (which came with your drivers) is also to be found in the configuration screen, like the "Avance AC97 Audio Configuration Panel" (note, the name may be different of course).