ok, the issue is either the motherboard has failed, or the windows installation is corrupted beyond repair.
To confirm this we will need to reinstall windows. If the reinstall works and the computer functions then it was the installation, else we know its the motherboard which would need to be replaced.
First though, this will remove all your data from the computer, so if you need to back up your data, in this situation, the only option is to remove the hard drive and put it into a different computer and try to copy the data directly via this. If your not able to do this, then you can have a computer store do this for you.
Once done, to do the reinstall of windows, you power off the computer. Then power it on and keep tapping on F11 until you get to the recovery manager, and then choose to do a factory restore, which will initiate the installation of windows.
If this fails to install then you will know that it was the motherboard and this would need to be replaced.