Just some thoughts..
Have you tried installing the latest sound drivers for your card? (Do you have a dedicated sound card or is it "intergrated"?)
Checked all the cables and their connections?
Could the speakers be fading?
If nothing else, maybe it's the sound card itself. They can "lose it" over time.
Hope this helps.
Just today,I noticed my volume output from my computer,is way down. I listen thru windows media player10,I checked at my control panel,the volume is at max,at the media player,it is at max volume too.
I use the speaker output,on the pc and feed it to the line in, on my stereo normally,I never need to go no more than half volume on the media player.
I have windows xp home,celeron cpu 1.70ghz,632ram
Any suggestions? Thank You