Stopped working,maybe some thing easy to fix,don't know much about them to look at it.

Imagine going to the doctor and explaining the pain in the back of your neck.
Now if you explain the problems with your desktop computer just like you would explain to your doctor, ie, did you switch it on, did you plug it in, is the monitor connected etc, the experts that Wiki has here will try and help you, honest.

I switched it on when it started up there was a bang and it went off,every thing else is working.

What went bang the monitor or the tower?
Have you checked/changed the fuse in the plug?
Have you checked all leads are connected correctly in case your power lead is arcing?

The computer went bang,as I said every thing else is ok,checked fuse,ok leads in tight.

Power supply unit. Take it to a shop if you can't do the job

Sounds like it could be the power supply unit (PSU) if it went pop and now won't do anything.

And all he wanted to do was give it away.....

Still willing to give it away for I have bought another one

I'd take it off your hands, I've got some repairs I need to do for myself and family members (and we're broke) so even if it's for salvage we would greatly appreciate it.

edit: I'm almost a month late, yikes hope you've still got it!

If you're anywhere in my end of wirral and you need a PC repair person for your new machine, I'm not too shabby, I'd pass you my number or e-mail.