Dell Optiplex 780 USFF and dual-monitors

I have a Dell Optiplex 780 Ultra Small form factor with two monitors.

I had no input in ordering this PC, so I don't know if it should be used for what I need it to do. That said, it is an all-in-one unit with a Dell 22' monitor.

The 780 has a DisplayPort & VGA port . . .  the monitor has a DisplayPort, DVI & VGA connector. Initially, when I was setting it up, it BSOD on me when installing the updated monitor driver. The system decided to do a Repair of itself. After that, it seemed fine.

When I got to the site, the user wanted to plug in a 2nd monitor. He had a VGA cable on the monitor, so I used that. Since then, it's been one BSOD after another.

What tree do I bark up?

• Do I do a clean install of the OS (Win7 64-bit Business)
• Do I troubleshoot the video card? (Of course, the video is on-board)
• What else?

Thanks for any ideas?