1. My Dad's PC
It's only a few months old but it was crashing after playing Fifa or Tiger Woods Golf for anywhere between a few seconds and an hour. First I ran a few memory tests, and tried all the driver versions I could. No luck. Then I tried adding extra case fans. After it worked fine for a while with the case still off I put it all back together, only to find it broke in a few seconds the next time I tried. So then I tried changing the graphics card, since it's only in graphics-intensive games that it crashes. It still crashed in a few seconds the first time I tried it. Then I took both out, put the old stuff back and moved the RAM chip from slot 1 to slot 2. It ran for 4 games of Fifa before I decided I'd had enough of it – it seems to be working, but only time will tell. The random problems are the worst!

2. My Router
After it's been used for a while, the wireless signal drops and the router needs resetting. I read that this is because of bad design, with hot components placed under the wireless module. So all day I've had a fan pointing at it. When everyone else went to bed I switched the fan off and came upstairs. Within minutes the signal dropped! Unfortunately I have no way of knowing if it was just chance or not.