Windows keep shutting down after posting

[dofunny]

Serial Number: 93fkt51
Model: DHS
Optiplex GX280

I bought a new flat screen monitor and plug it in when I got home and the computer been shutting down every since. I can hit the power button and it will post and soon after it post it shuts down. I try another power supply and it may it shut off still. I pull out all the cards to do some troubleshooting but still shutting off

[hot dog]

Does the monitor work in any other computers?  If it does not, then we've isolated the problem to the monitor... 

If it DOES work in other computers, then we've isolated the problem to your current computer..