My PC is: AMD Athlon64 3800 dual core, GeForce 7800GTX 256MB, 2G Ram, Asus A8N-E motherboard, Win xp pro sp1. Last week I heard a loud noise from one of my pc fans. At first I thought it could be my VGA fan (with my old computer I had to change the cooling fan twice), but after checking my Asus probe software I saw that the problem was labelled under "Power Fan", and it showed the fan speed dropping and rising as the noise became louder or quieter respectively. At this point I still was not sure which fan was malfunctioning, but it should be noted that my pc was otherwise working without problems. After a day I took it to a local computer shop to have it seen. They said that it was probably the CPU fan, and had to be changed, I agreed but had to wait a day. After the repair I took my pc home and tried out, I checked my asus probe and immediately noticed that the CPU fan speed was around 2000/2500 rpm while in the past it had always been over 5000. I also saw that the CPU temp. was at 45/47, again in the past it had been between 32 and 35. I decided to play a game to test it, but after only 5 minutes the pc shut down. I rebooted and saw that according to the asus probe the cpu temp was over 90, and had crossed the probe safety settings. I gave it another try, but the same thing happened, and this time I could still hear the same loud noise I had in the first place. So, I took the pc back to the shop and explained the problem and left it there because it was near closing time. The following day I returned, but they did not really believe the cpu fan or the cpu itself had any problems. They said that it was probably the asus probe that was faulty, because they had touched the heat sink and didn't feel any real heat problem. I was not convinced, the probe had apparently worked up to a few days ago, so why would it suddenly stop now. As I was talking to these "Einsteins" I tested the pc in front of them and we started hearing that same noise, which in the end the culprit turned out to be my chip set (nvidia nforce4 ultra)fan. So, the cpu fan I had before was functioning perfectly, and it was replaced fo no reason. Before I had one problem, now I have two. They are going to contact asus about the chipset fan, but I believe that the "new" fan has problems. What I would like to know is if che chipset is overheated could this influence the way the cpu fan works, or even the cpu? Because if the two things are not related then they must be to separate problem. Of course I am not a computer expert, so I could be wrong but my sixth sense tells me that if they put the old CPU fan back in, this overheating problem will go away. Let's also point out that my old fan was AMD while the new one is not. I'd like to know if anyone has had any similar experience or has any insight, something that I am missing. Are these probes reliable, are they only for reference. I just want to know who is right and how to fix my pc.