Just wanted to mention that at least part of the problem was that my Samsung 220wm monitor had abruptly gone bad in the middle of me working on a different vexing computer problem(the main partition disappeared) so I wasn't thinking about the funky power switch on the Samsung monitor which I think went totally bad on me. I can't explain why the 1 2 lights were on and then no longer on after I replaced the monitor.  It doesn't make sense, so in the interim I must have fiddled with something else that fixed that problem.  Maybe it was the battery replacement  or the resetting of the cmos. I really appreciate the help I get here on this forum, and I'm sure I'll be back.
    Optiplex 960 MT seems to power up but screen stays blank  Can't access bios(F12).  Fans are working, power lights are on, graphic card fan spinning.  Front power switch shows blue/green in circle.  Diagnostic LEDs on front first show 1 2 and about 2 minutes later change to 1 2 3 and then two beeps.  I tried disconnecting the hard drives, the dvd player, and changed the motherboard battery.  I tried removing the graphics card to see if the computer would boot past the 1 2 3 LEDs, but that didn't make a difference.  What to do next?
Optiplex 960 MT blank screen...Diagostic LEDS= 1 2 3 and two beeps