This worked on a Fujitsu Amilo PC after a new DVD Drive installed and running Vista Home premium 32 bit. No sound was coming out of the same pair of speakers used before the repair but all the system checks showed that Realtek was working. So I contacted the repair company and this was the fix:
Open Realtek manager then plug your speaker lead into the front headphone socket and your speakers should start working. Obviously you need a CD playing, and at the same time an info box will pop up. This box will show a list of line in/line outs and have a tick against the Headphone entry. This proves that Realtek is working. If it's still not working then I can't help you, but if it is:
Unplug the speaker lead and plug into the the Green audio connection at the rear. Your speakers will probably not work but this will bring up the info box again and there will be a tick against the Rear Speaker entry. Untick and then tick the Front Speaker entry, click OK, and your speakers should now work.
This confusing (to me) setup is because Realtek is configured for surround sound but getting the information seems difficult if you don't use and so are not used to surround sound. Obviously this has only been used for a pair of speakers but if you are having similar problems with surround sound this might help.