I'm currently fixing a computer for my mom's friend and may require assistance from more professional technicians. Here is my dilemma: The client said that her husband said that the fan was broken (he has knowledge of computers himself). I went and check the inside of the computer and it was quite dusty within as it is. Seeing the dirtiness, I used compressed air to blow out much of it before giving it a test run. After running it several seconds, it shut down by itself and there was an odd hissing or grinding sound coming somewhere in the computer. I think I've seen this situation before where the computer shuts down by itself if the temperature rises above a certain point (this was an AMD Athlon XP Processor) and I had thought was coming from the fan. Going with the signs, I swapped out the old heat sink with a new one (Foxconn, AMD approval for Athlon XP 2000+) using Arctic Silver 5 thermal compound, using about a tiny bit more than a grain of rice amount. The process itself is a learning experience for someone that hasn't dealt with the more heavier task such as processors and heatsink. I ran another test on the computer again and the same thing happened with the same sound heard when it starts up again. Listening closely, it was more oriented towards the Power Supply actually making my first presumption wrong. Now I have two possible thought: - The power supply is defected and needs to be replaced - The Heat Sink I purchased isn't enough and needs to be swapped with a new one. What I'm asking is people's thought and advice of this as well as possible advice on what I can improve on in the future. Thank you.