Inaudible sound

I have a new computer with WinXP installed. The unpowered PC speakers from my previous system are virtually inaudible on the new system even though all the volume controls are set to maximum. I have tested the speakers on the old system and they still work. The sound card is on-board. The chipset drivers have been installed. The device is ac97. It is enabled in BIOS and windows and there are no conflicts. The driver is signed by Microsoft. I am using the right jack-port and this is confirmed by the jack detector. I’ve used the WinXP troubleshooter a couple of times and no luck there. I am absolutely at the end of ideas about what to do – can anyone help please.