Temperamental Mobo/HDD?

[Snozzz]

If your BIOS needs setting every time you boot up then it pretty certain that the back up battery has failed. Replace it and see if it stops that behavior. I see you say the HDD works fine in other machines, so. Try using the WD diagnostics program, most manufacturers provide one, just go to their site and find it. Then test the drive on your problem PC and a known good PC. If it is just bad on the problem PC then your mobo is likey toast. If the drive is bad the test software should be able to generate a report for return under warranty if its still valid.