The beep errors have different meanings depending on the BIOS type. Since you haven't told us what board you have I'm not going to guess.
One can be graphics related, the other memory.
BIOS corruption and a Inaccessible Boot Device error 0x0000007b
Can you please provide your full system specs, board, rev #, BIOS and version, installed devices, disk configuration, operate mode of the disk controller, etc. The more information your provide, the better.
Did the PC ever work, for how long. Have you recently changed anything? What happened?
You have multiple, seemingly unrelated problems. Its strange how they all appeared at once.