Toshiba R940 gives blue screen or PXE-E61 Media Test Failure

I bought a Toshiba Tecra R940 last summer used online. Yesterday the computer started making a high-ish pitches buzzing noise in the middle of the usage. I continued using my laptop as normal, but later tried to restart the laptop to get rid of the buzzing. I haven't been able to login since. Sometimes my computer will open up to a screen to try to resolve the problem or open windows normally. If I do the first it works for about an hour and then says it can't automatically fix the problem. If I do the second it opens a blue screen. Most of the time I turn on my laptop it opens up "Intel(R) Boot Agent GE v1.3.81" and then says:
"PXE-E61: Media test failure, check cable
PXE-M0F: Exiting Intel Boot Agent
Insert system disk in drive
Press any key when ready . . . . "
When I press any key it gives the same error message. I've had this computer a little over a year now and have experienced no problems like this. Please help!!