The front panel (the thing with the USB & audio ports at the front) didn't really work so I decided to open up my PC and remove it.
It was obviously connected to the main board so I just unplugged it and took it out and now the sound on the PC does not work.
There is no error shown at all. The PC shows that there is sound coming out but nothing comes out of the speakers (which were always plugged in at the back anyway).
I assume I have to turn something off int he BIOS but I have no idea really.
Have you tried reinstalling the sound driver? The rear sound ports are not usually dependent on any other cables being plugged in to the motherboard. Perhaps simply the change in setup has somehow upset the driver.