no sound

I have a strange problem:

If I log in as root, I have all the Knoppix, bubbly system sounds.
If I log in as a normal user, I have no system sounds, but if I use xmms, I have sound.

I am using a Compaq Presario with Knoppix 3.4 installed (2.4.26 kernel because 2.6.6 doesn't recognize my mouse).

I tried all your suggestions, but I could not get sound on my user account to work. Any advice, beside logging in as root?

EDIT!

I did not try one thing, that is: REBOOT! After rebooting, TWICE, the sound worked. The first reboot caused a problem big enough that fsck gave up and said "Repair manually." By that I understood that it was time to go to bed. Rebooting again gave me all the sound and a new lease on life. Thank you for your help.