How do i completely clear a computer and start again?

my mother has given my grandmother her old computer but it turns itself off and the monitor keeps saying no signal, so i figured if i clear the whole thing and start again it may fix the problem, how do i do this?How do i completely clear a computer and start again?
Reformat.


BUT if it's powering on %26amp; off by itself, you may need a new power supply.


1st try opening the pc %26amp; cleaning out all the dust around the vents %26amp; on the motherboard. If that doesn't stop it from power issues, then it is the Power SupplyHow do i completely clear a computer and start again?
No, the problem is a bad power supply most likely. Either take the computer to a shop and have the power supply replaced, or open the computer up, identify the power supply and buy a new one and install it yourself. A ';no signal'; itself is an indication of a bad video card, but if the computer shuts itself off and then says no signal, then it is the power supply that is the cause.





Replace the power supply unit.
If the computer turns itself off immediately after startup, then you should try starting it up in safe mode. You can do this by restarting the computer and repeatedly pressing the F8 key. If that doesn't work, I would recommend you reformat the hard drive, which can be done when you install a new operating system. All you need to do is install the new operating system and tell it to use the entire drive, which will reformat everything (clear the drive).
The fact that it turns itself off means that there is a problem with the hardware, so clearning the hard drives wouldn't affect it, unless it turns off while its loading or has loaded the operating system.





If you do want to ';completely clear'; it then you will need to get the operating system installation disk, and then ask it to format the hard drive.
format it with the service pack disc, be for you start, press ctrl%26gt;.alt%26gt;delete together, to enter the biops, chang boot up to CD Rom press f10 to save change then enter to leave.. now put in your service pack disc, and follow the instructions
You may be in trouble if its fairly old cos you need the installation disks and the drivers for sound, video, modem etc check that you have these before you start to re-format
Without knowing your operating system or any other information all the answers here are worthless. You need to provide more information, desktop or tower is the monitor properly plugged in, Is the graphic card on board or PCI/AGP? As much information as possible
Take out the hard drive and get a new one. I'm pretty sure its not what's on the computer that's the problem though. It's probably just not compatible with the monitor.
It is a hardware problem. Either one of the fans doesnt work, or its the power supply.
Reformat.