Thanks again for all the help.
An update for anyone who cares. I tried all of the usual things....and a few creative ones....and not a dickie-bird. Whilst I'll admit to being a bit geeky and do enjoy beating the machine, the this afternoon I decided I couldn't justify the time I was spending playing with it (OK, I had some help in making this decision!) and went out and got the cheapo card. It installed beautifully, albeit the instructions didn't help much, and makes a perfectly acceptable noise. And it cost less than sending it back again.