My speaker output is shot but all indications are fine

Windows Vista 64x, with integrated motherboard audio.

The output through my speakers has become very, very weak, even though all the connections appear fully functional when I test them withn both Realtek and Windows audio manager.

I have tried switching from 5.1 to stereo, etc., and played with the output settings, to no avail.

System volume is set at 75% as it has always been.

Audio output via my USB headset is unaffected and good as ever.

This is distressing me. I fear it may be a hardware issue and that I might have blown my speakers somehow. I do not over-stress them but they are Altec Lansings, about 6 years old.

Can anyone suggest a way to troubleshoot this, short of replacing all four speakers plus sub-woofer?

Many thanks in anticipation.

What if you plug the speakers into your stereo/ipod/phone/etc*? That will at least confirm/rule out whether the issue is with the computer hardware/software vs a problem with the speaker hardware.

Many thanks for the response, linoleum. The speakers are not USB but dedicated PC speakers so I don't think I can plug them into another device but I am going to test all the connections, reinstakll the driver, check the fuse in the sub-woofer...and then buy new speakers if necessary.