grub fails to load, giving error 15, after I unplugged my IDE drives.
 

I recently installed a new PSU due to the old one being badly on the blink, and unplugged all my IDE drives in order to do that - at the time it made sense, the cables were really in the way. After plugging them back in, however, I now find that Grub exits before it even really enters (I don't even get to pick an operating system, it dies as soon as BIOS hands over to it) with error 15 - to my understanding a file not found error.

I suspect this is rather because I plugged the drives in differently to when I unplugged them, so I think that, for example, "sda1" now no longer points to physical drive its supposed to. Is there a way to a) find out what my drives are now, and b) edit Grub so that it knows where everything is?

Or is the easiest solution just to try different IDE combinations until I find the one it was before?

Thanks in advance, and I'm sorry to waste your time by essentially being too much of an eejit to note down how I'd got them installed before :)

Obviously it will depend where your grub was and where it was supposed to look for the operating system. If you do not know where you connected your hard drive then only way is swap them and see if your system boots. Otherwise you can use the system rescue cd to boot with it and find the exact geometry of your drives. If you get to grub prompt then you can use geometry command to find out about it.