during this few days,my pc keeps on shut off by itself after i on it for about an hour.after the pc shut down,i found that my power supply become very hot.to identify what is the problem,i had downloaded the asus pc probe software and it detected this problem:"power fan is under threshold". So, does this message means something wrong with my power supply or the problem came from another peripharals?

It is pretty likely that it is your power supply, but it sounds like it might be the fan in your power supply that is supposed to cool it. If you feel competent to do so, put in a new fan. If not, get a new power supply. Either way, avoid running your system until you deal with it.

Budfred

most likley going south,how old is it, and it depends on what you have hooked to it, and how much, what is it rated for? and what have you added to it, is the fan running at all?

Providing adequate cooling to the power supply could help. But it is getting heated up after running for an hr or so, I suggest a repair/replacement.

Most power supplies do include some form of thermal protection, a common method of thermal protection is to turn the unit off if the temp gets too high. You problem seems to be following this pattern, the PSU heats up, the computer shuts off, the PSU cools down, you can start it back up.

Yes, it is time to replace the power supply.

The problem is most likely the fan, which can be replaced for under $15 (more if you have a shop do it), but if this has been happening for a while (more than two or three times) then there is likely to be heat related component failure in the power supply itself (the capacitors will definitely creep out of spec under high heat, and they won't go back, they will have permenently changed value). Replacing all the individual capacitors in a power supply will get very exepensive...

So it will probably be cheeper just to replace the whole thing.

had changed the power supply just now and currently everything is fine after testing the computer with a game for few hours.thanks a lot for your help.