I have a laptop that has a much lower audio output than it used to. Its a compaq Evo running XP, and now when i crank all settings to maximum i can still listen in headphones without it being too loud.
The problem started after somone else used the computer, presumably after he pressed the hardware volume settings on the laptop case.

I have checked the visble volume sliders available in XP, activated all settings i would wanna try, disactivated all line in and such. Yet the sound is very weak.

This goes for mp3 playback as well as video files.
The computer does have ac3 codecs installed, i reckon.

I have tried booting the computer into (knoppix) linux, and then the sound levels were high as normal, which leads me to believe that this is not a hardware problem, but perhaps some very well hidden setting in Windows, or some file that has been changed.

Any ideas ?

cheers

Surely you're right. I have knoppix, too; it doesn't use anything from the hard disc. Obviously your BIOS is still OK
Regarding your problem, I hope you have a backup...

W0000t ?

I don't understand your post...
Backup means that, if I was you, I'd try to revert my PC to a status in the past when it was still OK (if you have installed such a program)
or, if you have a copy (backup) from your hard disc, overwrite the current hard disc data with the old one (from before the problem).
These are the general procedures for solving software problems.