I just put a new Motherboard in a Dell e521. In the Bios "Boot Sequence" menu the Bootable Hard Drive has no number in front of it so moving it to the top of the list does not make it number 1 . . it remains un-numbered. So, the computer cannot find a bootable device.
However, if I push F12 to enter the boot menu, I can select "Bootable Hard Drive" and the computer will boot.
Solution: I reset to Default Settings and then it worked. Sorta of strange because I had never changed anything in the first place. It was a brand new board . . it had no Service Tag number configured.
it's a simple change in the BIOS settings, you have to use the correct button on keyboard to make the change you wish.
off the top of my head (memory) I do not have my Dell anymore; I believe you have to make that change with the space bar to activate.
I might be wrong.
all you have to do is pay close attention to the dialog box it will tell you how to do it.
if you can't figure it out I will go to a Dell unit and redo the process to refresh my memory and then explain it to you..
Thanks for you reply, but the Default Settings caused the drive to be "numbered"