Well, it's looking like hard drive failure is the most likely problem. Will update when I get a chance to check it out.
I recently reformatted my friend's computer that was riddled with viruses, etc. The virus protection installed on it had been hijacked by a virus, so the computer was totally open to anything and everything for months at least. After reformatting and rebooting a few times, the computer was running fine. However, a few days later after rebooting, the hard drive stopped reading entirely. It doesn't show up in the bios at all. The pc is a newer model Asus bought within the last couple of years, so it makes me doubt hardware failure. Also, from my understanding, even if a hard drive fails, it is typically still readable. I haven't been able to check out the pc yet myself, but as soon as I do, I'll make all the usual checks for connections, etc. The pc was also not touched after reformatting, so theres no reason why it should be a loose connection. I'm aware that biosviruses are very rare, but being as it was totally exposed over a long period of time with constant internet connection, I consider it a possibility. I've also not heard this to be a symptom of any bios viruses, but I do hear they can easily leave a pc totally incapacitated. Thoughts, suggestions, ideas are greatly appreciated.