Hi~my computer won't start. It froze, and when I turned it off it wouldn't start again. I've tried inserting windows disk to re-install, but nothing shows on the screen (the screen is fine and functioning). I think there is a problem with the disk reader. Can I install Windows Vista on to an external hard drive (using another computer of course) and maybe the thing will start up from the external drive when I plug it in?

The external hard drive would need to be setup as bootable. You would need to go into your computer's BIOS, normally pressing either F2, F12, or DEL when you turn it on to get in the BIOS and the do the boot sequence. Ensure that you place something like external hard disk at the top of the boot sequence list and then your computer should load from it.