Has this just started happening on a working machine, or are you trying to get a machine working? Check the settings of the PSWD and BIOS jumpers - they are usually set with PSWD jumpered and BIOS off.

It was working yesterday, before I changed the BIOS setup. The internal sound card was not working so I checked BIOS and it was set to OFF. So I changed it to ON, and also enabled internal speaker.

Alt+b or something, it rebooted and hanged. Showed Optiplex logo and F2 to enter BIOS setup(maybe working slower than normal), for a while and hanged with a blank screen. I pressed F2 during bootup, but nothing happened.

Then I might have done something stupid, but I figured out it should reset the BIOS setup, so I took out the battery for a couple of minutes and started up again. Then I got the message that "Cover previously removed", "Ivalid configuration information - please run SETUP program" and Time and date not set. Then it stopped.

Next reboot it didn't show the last msg (time and date) but only the two other msg. After trying pressing F2 and Ctrl+alt+enter I went for the jumpers. Moved the one from PSWD to BIOS and back. Didn't seem to have any effect at all. So now I'm stuck for ideas...

Problem partially solved. It was some HW problem, I took it apart and put it together again, and now it works. Hurray! :)