nivethanansivachelvan :
its saying to insert boot disk and press any key but i don't know what to do?
its? What is that? A laptop? Desktop? Is this the first time it happened? Were there any upgrades?
The easy fix is to restart, enter your BIOS(spam F2 or Delete at power on and change the 1st boot device to the appropriate drive. That will only work if the hard drive/SSD is still working.