First thing is to run diagnostic on it. When you press the power button start tapping the F key that is for your puter and the BIOS menu will open. Select diagnostics if you have one and test everything to find any errors. Not all system have a diagnostics in the BIOS. If the hard drive fails or it says you do not have one then you're going to have to get a new one and order the recovery DVD from the manufacturer. If everything passes, it sounds like the OS is corrupted. If you have a system repair CD or a Windows install DVD, boot from the DVD/CD and run repair from it. You will have to access the boot device options in the BIOS to make it boot from the DVD/CD. If you do not have a system repair CD you can make one from a puter that has the same OS as yours. If that does not fix it then your probably going to have to reload your OS to get back up and running. You will need to recover your data and files before doing that. If you wish to try to recover your files go to the link below and read on how to download and use a Linux Live CD to boot the system to recover what you want. If you have a Windows 8 puter then you need to turn off secure boot before using the CD. The Live CD will also allow you to check out the rest of the puter.
http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/
Once you have recovered what you need you can reload your OS.
Try Advanced boot options. When you press the power button, start tapping the F8 key. You will see the advance boot menu. Select repair your computer. Select your language and then enter your user name and password. Then click on (brand name) factory Image Restore and next. Answer the question and it should start the recovery back to factory settings.
If you can not access the advance boot options then try recovery from the recovery partition.
When you press the power button start tapping the F key that is for your puter and the BIOS menu will open, select the recovery mode. This will reset your puter back to factory settings.
Manufacturers BIOS menu F key
HP/Compaq ESC
Sony F2
ASUS Del
Gateway, eMachines F10
Acer, Dell, Fijitsu, Gigabyte, Toshiba F12
This is what a BIOS menu will looks like. Yours might be different, I am posting this one to give you an idea of what to look for.
F1 = System Info
F2 = System Diagnostic
F9 = Boot Device options
F10 = BIOS Setup
F11 = System recovery