[chicha]

i had a similar problem.
what did you do last?
was there any BSOD?

you said its showing in bios then the HDD.
Plug out the HDD and then run the pc, the next time you restart connect this HDD.

when it happend to me it was IDE's fault, try changing it.
and also connect this hard disk on some other system to check if its working.
or simply disscount the other hard disk and connect the one with the problem.