I'm out visiting the in-laws at the moment. My father in law has a computer which he finds very useful, but a couple of weeks ago it broke. It started displaying strange messages on boot up and after a chat on the phone we decided that it was hardware. So he called in a chap who advertised in the local press as a computer fixer. This "engineer" turned up and took a look at the machine, agreed that it was broken, said it was too old to repair/not worth mending and then asked for 25 quid call out fee. Which he got (having rather presciently not advertised a no fix, no fee policy). We took a look and found that it was the power supply, dropped in a replacement and the machine woke up and ran a treat.
This is a truly nasty little business. It was very obvious to us that the power supply was wrong (if the BIOS reports 4.3 volts on the 5 volt rail the number of suspects is somewhat limited) and so I'm inclined to not give this chap the benefit of the doubt. So if you are calling someone out to mend your hardware you should make sure that they are no fix, no fee operators.