First, I assume you have made sure the speakers are in the right plug in spot on the sound card. I know, that would be the obvious, I am not trying to insult your intellgence in anyway, just checking.
Next, if you right click my computer, and click on properties. Then go to the device manager tab, and you click on plus sign next to sound, do you see any yellow exclamation ! marks next to anything in there? this would indicate a conflict on the sound card itself.
If it is a new compaq, and you check both of those out, then your best bet would be to call compaq tech support, assuming it is under warranty. They should be able to walk you though fixing it if it is a driver issue, which it usually is.
also, don't be suprised to find yourself having problems with your modem if you have a compaq with an hsp micromodem... those are one of teh worse 3 modems ever created... along with rockwell and conextant. If you are lucky enough to have an LT winmodem, then I would definately be relectant to give back the computer for another one, at least not without insisting you get an LT winmodem installed (or anything other than that hsp crap).