How do I fix this computer error: Operating System Not Found

The following code has been copied from what I think I'm reading from the screen on this video.

-[Repeating Error Message begin]-
For Realtek RTL0100E/0101E Fast Ethernet Adapter v1.02 PXE-E61: Media test failure, check cable
PXE-M0F: Exiting PXE ROM.
Operating System Not Found

Intel UNDI, PXE-2.1 (build 082)
Copyright (C) 1997-2000 Intel Corporation
-[Repeating Error Message end]-

This is occurring on a Toshiba laptop computer with Windows Vista Home Premium pre-installed. The error began while trying to press F-function keys (i.e. F8) to enter Safe Mode because the computer kept sporadically shutting down in the middle of any operations including start-up. Now this message is the only visual dialogue that occurs when the computer is turned on and there is no reboot (aka: re-boot) disc to load and set off in auto-pilot.

*UPDATE!*
The laptop was recycled because a solution was never found and it seemed less expensive to replace the computer than to have it repaired after technological advances consider it obsolete. Such is consumerism.

If you are still receiving this error, please read all comments before posting your comment asking if there is any way to fix the error, list which solutions you have tried, then consider commenting if none of the solutions have worked.

This problem may have been caused by shock; dropping the laptop computer, or hitting it somewhere that causes the electronics inside to possibly become dislodged or unplugged, and requiring a physical dissection and repair.