type of the error differs from the BIOS manufacter & sometimes the mobo manf.
beeps can occur due to,
ram failure
vga failure (this is if U have external vga)
some other critical failure.
normally for IDE failure BIOS doesnt give error tones.
Since you've said PC it leaves out the dead battery thing which can be in a laptop.
IDE's or other stuff (pci , usb.. ) are not necessarily needed for pc to boot up to BIOS program. So normally failiing either of them wont result in a error tone.. you should keep that in mind & start working on the first 3 options.
oh & one other thing, beeps can occur due to fan failures or overheating scenarios that is if you have them configured such in the BIOS options.

But these cant be the reasons since you cant boot up @ all.
Cheers,