Computer Repair Place...and weirdness?

So about two months ago my dad took my computer into a place his friend told him about to get it fixed. I suspected the issue was a fan. According to the guy, it was just full of dust, charged me $25 and sent me on my way.

I got it back and he had changed all of my settings. Wallpaper, location of task bar, etc. Didn't think any of that was necessary. Yesterday, I found a program on it called Prime95.

http://en.wikipedia.org/wiki/Prime95

This obviously isn't something I put there. I'm not computer illiterate, but I don't know anything beyond the bare bones to keep my machine running smoothly and free of viruses. Prime95 seems a little techy for me.

In short, what the hell is this program and why did he put it on my computer if all he did was vaccuum the thing? Also, is it currently doing anything? Like, if he needed it to test my computer or something...why did he leave it on?

Ohhh, must've been a mom'n pop shop. Careful of certain places.

Standard procedure for most places is that EVERY computer gets diagnosed for stuff. They probably ran an automated script. And I can tell you what Prime 95 is and why it was there.

They needed to know why the computer was overheating. So they used a benchmark program (Prime 95 does lots of complex math and tries to break your system. An overheating system will lock up). If the benchmarks pass then it's a software issue. Your probably failed, they blew it out, then it passed.

In short, they used Prime 95 to test the machine. But they should've just taken it off since you wouldn't know how to use it.

OK, sounds good.

I'm still not going back there. He said when I brought it in that he knew it was the dust. Then he changed my settings? Grrr.