I figure that I can't buy a ATX case which is what I wanted, because I have an BAT board. Failing this, I have decided just to get a new power supply which I need anyway.

The power switch on my case is an old AT one with 4 wires. I think the ATX ones are two wire connectors like, say, the reset switch. What are the chances I can convert the old switch to this new connector, and how? Has anyone ever done it?