Technotiger: Thank you for your quick response. My daughter has just bought a new graphics card for her spare PC and it says the PSU should be 450/500. So installing shouldn't be a problem?. She just plays games on it.
There are different power plugs for ATX system or should be an Adapter with it. But if it's not a Proprietary system like Dell etc then a ATX power will fit if it is a newish computer not years old. They used to be AT power supplies but you would have trouble getting on today. also if it's a Intel CPU you need one that has the four pin support plug also