Many thanks for all the replies, the problem (I think) was with the Sapphire brand of motherboards, they didn't seem to be able to cope at all with installation of seperate sound & graphics cards.

I was given two different Sapphire motherboards but still experienced the same problems with the Creative Soundcard.

After much much more complaining and a some bartering I've now got a spanking new Aopen motherboard with much better specs.
I did a complete reformat, then installed everything myself and HUZZAH! It all works, I now have perfect sound and treated myself to a lovely new graphics card.

In some cruel twist of fate, the CD-RW drive was broken in transit so that's being replaced tomorrow, when I get round to it and hopefully my run of bad luck with the new PC is over.

Thanks to everyone who offered help and solutions