Yesterday I was cleaning out the heatsink and fan of a friends laptop. Everything went well while we were taking it apart (although I wish I'd found the tomshardware guide before we started). Anyway we clean it out with compressed air and reassemble it, and now it won't turn on at all. When we connect it to the mains the LED indicating that the battery is charging is on. I'm completely stumped.
Well, I would disassemble again and look for loose wire connections and/or missing screws floating around in the chassis. Its apparent the power is getting to the pc with the led on.
Alot of times simply reassembling can make problems go away.