It could be the hardware fault

Reformatted the hard disk and the problem still exists?
If you are experiencing problems while running PC and you try to solve it by uninstall some suspicions software but it doesn't work .Finally,You though reformat your computer and start a fresh Window.

This will most likely resolve any software issues, remove those viruses or any other natives and give you a clean start. But what happens if you have already reformatted and the problem still exists?

It could be the hardware fault
Apparently, you have a hardware fault. This is where problems occur.
Diagnosing a computer hardware fault can be a right pain as any of the computer components could the cause. Unless you are intending to replace the entire machine you need to carefully diagnose with what components the fault lies with.

These are few areas most frequently happened fault.

1.Memory / RAM
Memory – this is fortunately quite easy to diagnose. Search the Internet for a memory tester.Visit "Memory Tester Tool at no cost" for the free software.Generally these can be put onto a CD ,boot up from the CD which then enters the memory test. This will constantly cycle through, testing the memory for errors. It is wise to leave this on for several hours or even better over night. It will advise you if the memory fails.

2.Power Supply
Power Supply – Most people don't even know this.people generally assume that if the power supply does fail then you would start you computer at all. This sometimes is not true.In fact,When computers turn off at random times, and computers that have the power light on, but do not start up,Also the blue screen that appear during start up, etc .it has turned out to be the supply –Testing it can be difficult without the right equipment. Really the only way is to get a volt tester and check the voltage and current coming out.If you/friend have another PC ,Just borrow the power supply unit to have a try.

3.Hard Disk
Hard Disk – this can be one of the worst problems , unless you have been sensible and done regular backups of your most valuable data, you stand to lose it all. Hard disks can go at any time and usually you will hear a harsh sounding clicking noise that is coming from your computer. If this is the case you need to probably replace the hard disk. Get someone who then knows what they are doing here to try and recover your old data for you.Don't even think to get your hard disk fix by checking the component inside by your self..It will destroy the data with no change to recover any data when it explore to the air.Get the professional.

4.System board
If none of the above solves your problem then most likely the fault being with the motherboard or any other plug in cards or devices you have. Remove those devices one by one to test whether it is cause by the plug in. Take out those sound cards etc and any other PCI devices that are not essential. If you have more than one stick of ram then leave in only one and see if the problem resolves.
This isn’t a complete definitive list, obviously depending on your issue ie if your issue is that you don’t get sound then it could be a sound card issue, similarly if you don’t get a display then graphics could be the culprit. If it is a random fault then either of the above could be the cause.