Some TV station in the US (KCal 9 if that means anything to you) did a Today Tonight style investigation into computer repair fraud, segment below thanks to Youtube.
All they did was unplug the IDE ribbon cable connecting the hard drive to your motherboard (the bit that co-ordinates all the functions of your computer). It is a pretty easy issue to pick up. First of all, when you turn the computer on, you could be greeted with a message saying "Hard disk fail" or equivalent. If so, first thing I'd check is the physical connection of both the data cable and the power cable, before suspecting hard drive failure (which has happened to me before but is rare) or power supply failure (quite unlikely). As a double-check or a further diagnosis, I would put the hard drive into another known, working computer and see how it goes.
Assuming that you don't get the "Hard disk fail" message, which may occur as some computers allow people to run them without a hard drive, e.g. they can boot using a CDROM and store data on a USB drive, or even boot using a network image, you would be given a 'no boot device found' or 'failure to boot' or a freeze when it gets to the booting stage. Its a bit harder to diagnose now, because there are many more data-related factors now, apart from the hardware/connection factors above, including hard drive boot sector corruption, physical data corruption and operating system corruption. Not to mention the stupid 'oops, I left a standard floppy in the floppy drive' mistake too - trust me, it happens more than you think, especially when you have a black case with a black floppy drive and a black floppy disk. In this case, I would understand why they may have to go to a bit more trouble, but given that complete hard drive failure is quite uncommon (I still have a working 250MB Connor hard drive sitting in the cupboard
), after realising that your troubleshooting boot disk isn't finding the drive at all, your next step would likely be to open the case.
As an observer, you may miss the un-connected IDE ribbon cable plug as each cable has three plugs, and not all have to be used. But for someone supposedly in the know, he/she should breathe a sign of relief when they see that.
I don't know how the Geek Squad people honestly reached the conclusion it was the power supply. After all, I'd assume if you thought it was the power supply you'd check to see if the hard drive was connected to power first, and at that point you should see the un-connected IDE connector on the hard drive. I guess geeks have a tendency to be lazy yet still make money, which if so, the power supply is a wise decision as they aren't dirt cheap, especially ones for older computers, yet there's no impact on the data on the drive at all, so they don't have to bother with reinstall drivers, recovering data etc.
The next guys at Circuit City worked out the issue, tacked on a closely-related non-issue (an incorrect jumper set) and managed to charge US$59.99 for the work! Geez, a quick calculation with Google tells me that's a bit over 76 bucks in AUD - hell, I can't believe people still work at Macca's these days! Wait, it gets worse though...
CompUSA was the next target, and were smart enough to work it out. I guess they either had they money to hire some good technicians, offers absolutely awesome customer service, or had greed pumping through their veins - they charged US$119.99 (it is their minimum charge though, but good customer service ethics tells me you should make an exception here). Converted to AUD, that's a bit over 152 bucks, all for plugging a damn bloody cable in! I guess geeks are expensive to keep given they require special care (coffee, pizza, computer and unfettered access to the net), and are likely to blow up your shop's computer systems if you piss them off.
The next place to be tested was Fry's, correctly diagnosing the issue but charging US$69.99, translating to a bit over 88 bucks AUD.
The place after that was the only decent place tested - they fixed it, and charged nothing. Now there's a lesson in customer service.
The last place was just ridiculous - there was a power short-circuit? I'll admit, it does happen - in fact, I have a dead motherboard sitting here most likely due to that. But geez, how the hell did he come to that conclusion in that case? It wasn't even a smart conclusion to make up, given the effort required to replace the power supply and motherboard as he claimed needed.
Imagine the money I'd be able to make if I got a job as a PC technician. Hell, with some of the diagnoses given above, anyone can be one. Its boring as all hell, but hey, who actually enjoys working at KFC? With computers being more and more prevalent in society, the need for technicians is going up and up...
Like one of the comments on Youtube said, computer repair shops are going the way of car mechanics.