|You could have a hardware problem like bad memory or even more likely a hard drive that is dead or dying.|
Try booting to a Live Linux distribution via a DVD or Puppy Linux which can fit on a CD (do not try to install, just boot to it). If it boots fully then that proves that your CPU, motherboard, and probably the memory is good (more on testing that later if needed). Then while you are in Linux try accessing your hard drive to see if your files are accessible. If access is good then your hard drive is probably OK, if access is difficult but you can see and copy files, even with effort, then if you do not have a complete back up, Immediately copy all important files to an external drive because the drive is probably on its last legs and could dye at any moment. If you cannot access the drive at all then the drive is probably gone.
Run Memtest 86 via a bootable CD to test your memory, especially if there is any doubt that it is good.
Run your hard drive manufacture's test utility or Seatools from Seagate (bootable CD) and run the short hard drive test (non-distructive test) which will totally evaluate the integrity of the hard drive.
These all can be downloaded and you just burn the ISO image onto the CD/DVD on another computer and boot to it.
You should not even need F8 (advanced boot options) if the BIOS is set to boot to the CD drive before the hard drive but you may need to 'hit any key' when prompted.
If you still cannot get into any boot option or these tests (or especially BIOS set up) then it could be your memory is completely bad or you may have worse problems like with motherboard, CPU, or your power supply may be just putting out much too little in the way of current to fully load anything.
Try what you can and get back to use with results which may point out which way to go from here.
You have to be a little bit crazy to keep you from going insane.