What must i do when my pc condition is this?

I Think the some wire may come in to the CPU fan open the case and find out from where this sound is coming. If you did not find anything strange then i suggest you to take the computer to hardware engineer.

It is most likely either the hard drive or a fan. First thing you should do is back up all you critical data which you should have done already anyways before taking the back off. With the back off determine where the noise is coming from. The source could be coming from the hard drive, the cooling fan on the cpu or the general clearing fan. If it is a fancy high end computer you might have additional fans. When you fire it up with the top off it will probably be immediately apparent where the noise is coming from. If not use an empty paper towel tube to listen to the different components. If you are lucky it will be a wire that has fallen down onto the fan blades so just secure it. If it is dirt, use a vacuum cleaner and a soft paint brush to dislodge the dirt. Be careful. you do not want to dislodge anything like plugs or you will have more problems. If there is no apparent reason for the fan noise it is probably the bearings are worn or dried out and usually a replacement is the only option. Sometimes you can disassemble the fan and lubricate the shaft but this is only a temporary solution. If the whining is coming from your hard drive you are in trouble, it is on its way out. You need a new hard drive. If you buy a new hard drive it will probably come with some sort of duplicating software. The software will make a duplicate of your exisiting hard drive as long as the old hard drive is still working. Do not leave it too long. If you do not like poking around in your computer you will have to go get an expensive repair. This problem will not fix itself.

Yes friend THe cause may be a wire touching the CPU fan or it may be your hard drive which is going to its end if your hard drive if not more than 10 years old and you havnt formatted it at least 50 to 70 times then dont worry there may be any other reason such like your system is not set to earth to reduce charge by an earth wire in your plug...!!!