Open msconfig and make sure Safe Mode is not selected on the boot tab.

i have the same problem with the monitor on the DisplyPort

when i start the optiplex 790 and turn the monitor later it wont come on (power save mode- no power on the connector ditected)

when i start the computer with monitor turnd on there is no problem

when the computer is loged on and i exedently triggert the powerbutton of the monitor i get 2 different problems (random), somtimes the monitor wont come back (power save mode- no power on the connector ditected) or it will come back with a different resolution (1280*1024 when is whas 1680*1050)

i have tried a newer vga driver directly form intel and the problems for exedential triggering the powerbutton is gone

the powerup broblem is still there.

Optiplex 790 sff

p2210 monitor on Displayport

Windows XP sp3

Install the monitor driver and make sure windows can see it as something other than Generic monitor.

http://ftp.us.dell.com/monitors/DELL_P2210-MONITOR_A00-00_R217928.EXE

Tried all  no joy ---Thank you all for help, but PC motherboard was one of the issues had to be changed--problem solved