Switching the power on a drive is not a good idea. If you have two drives on an IDE cable, and you disconnect power to one of the drives, it messes with the termination on the IDE channel, which can make for data corruption, or more likely, poor throughput. It can cause a bunch of trouble, and really mess with the IDE controller. If you’re not going to use either drive on the IDE channel, it will be OK. I suggest getting a double pole single throw switch, and use a covered switch to avoid accidental switching. Either that, or use a key switch, and a relay to control the power to the drives. Not only can switching the power while the puter is running cause it to freeze, it can damage the drives, and the IDE controller! Most of the time, the drives and the mobo will be fine, but sometimes, it can fry stuff. It can cause the machine to fry, I’ve had it happen. Not only that, but the drives weren’t designed to be powered while the machine is running, so the sudden load on the PSU can cause it to shut down’ or the power on the 12v rail to dip, or worse, SPIKE! This is why it can toast stuff, rapid voltage transitions can cause big problems. So, make sure you NEVER hit that switch while the machine is running. Covered safety switches, or a key switch with a relay, or possibly a double pole key switch would be ideal. Allthough, I’ve never seen a key switch that is double pole. Good luck, hope it works. I don’t live in the UK, so I dunno about a source for parts.