Computer security in general are pretty pointless (no matter what OS) if some has physical access to the computer.

You make it sound like it is only Windows that has this problem. Computer security in general are pretty pointless (no matter what OS) if some has physical access to the computer.

in exchange for a home-cooked meal (or beer & pizza)

I had an acquaintance who claimed to have worked as a computer tech for a school. He said he used to steal memory out of the computers, and install viruses so he'd get called back to remove them. I assume there are still people like that around. And even if they're not criminals, they may be incompetent. I've seen far too many computers bought from local stores that were assembled improperly and doomed to fail prematurely.

Shady mechanics inspired me to fix my own car when it was broken

I repair PCs in my bedroom, got turned down by a lot of PC repair shops even after demonstrating my talent for repairing just about any problem while retaining the data on the computer. 90% of the repairs I've done in the past 4 years have been to fix problems that arose from the Best Buy Geek Squad "repairing" a computer. The worst instance was one guy that called the Geek Squad to have a Dazzle adapter (hook tv/vcr up to PC) set up, all the Geek Squad attendant had to do was pop in the disc and press Ok about 7 times: they wiped his PC clean because of "spyware", didn't install any of the drivers for his PC (which were also on an easy install disc), and then charged him an outrageous amount. I used a data recovery disc to revert the reinstall, luckily only a small amount of data wasn't recoverable and that was one of many games the guy bought online and didn't have a disc for. It had only minor spyware on it, so minor that a single scan of spybot cleaned the thing up as good as new, though I did use a couple others to make sure it was clean. Took maybe 2 minutes to set up the Dazzle adapter, another 30 to record a show, then about 5 more minutes to burn it to DVD, all while walking him through the process so he understood how to do it on his own. The guy was so happy he handed me $50 before even asking about repair price, which I told him for something that went so easy I only charge $30 at the most, and only ever charge more if there are complications that make repairs frustrating.

70% of PC repairs go easy, so easy that you could probably get away with searching google for a fix and do it yourself. Hardware takes a bit more knowledge but even then the information is so easily accessible that it's not difficult at all to teach yourself to fix a PC. Though I may be bias in saying that as I grew up building and repairing computers, started on computers before even entering the mandatory education.

Good read. I'd like to get into computer repair for myself to pick up some extra cash, but I can't help but worry about messing up a customer's computer if I did it. It's that thing where you feel comfortable doing something all the time for yourself, but when it comes to doing it for someone else, it's just nervewracking.

Tried cracking a password on an Active Directory?

John the Ripper : A powerful, flexible, and fast multi-platform password hash cracker
John the Ripper is a fast password cracker, currently available for many flavors of Unix (11 are officially supported, not counting different architectures), DOS, Win32, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. It supports several crypt(3) password hash types which are most commonly found on various Unix flavors, as well as Kerberos AFS and Windows NT/2000/XP LM hashes. Several other hash types are added with contributed patches. You will want to start with some wordlists, which you can find here, here, or here.

THC Hydra : A Fast network authentication cracker which supports many different services
When you need to brute force crack a remote authentication service, Hydra is often the tool of choice. It can perform rapid dictionary attacks against more then 30 protocols, including telnet, ftp, http, https, smb, several databases, and much more. Like THC Amap this release is from the fine folks at THC.

http://sectools.org/crackers.html

You cant really say that all techs are like that I myself being a computer tech would be considered an honest tech and it even took me many years to find a good place that has values and pride in what they do and would be willing to hire me lol. There are places out there most people would over look because it might look run down or even not trust worthy but it would still be in your best interest to study up a little on the problem a bit or even the place you might be willing to go and see if the person your talking to might have half a clue into what he/she is doing or is talking about oh and please I know most people know this but leave the attitude at the door it has a tendency to cause more harm then prevent it. I cant say I'm outraged by this topic I know that there are many many horrible people out in this world while the few with honorable intentions get screwed hard, so please don't go around thinking that when the time comes to fix your computer that all the techs are out to screw you or do something bad to your system, also if you have a part replaced they should give you the part they had to pull out and replace as proof like we do in the shop I'm at.