OptiPlex 755 Video problem

I am working with a DELL  OptiPlex 755 X86 Intel processor running Windows XP Pro.  I thought the video monitor went bad and added a new one that worked for a few days and went dark.  Tested the monitor on a different PC and it works fine.  ( a new ACER)  The display works in bootup and in system setup mode  I tried safe boot but the PC hangs in startup. I can Remote Desktop to the PC and everything appears to run properly.

When I check the hardware Device screen, the:

• PCI Serial Port
• PCI Simple Communications Controller
• Video Controller
• Video Controller (VGA Compatible)

all show as a problem.  I try to install drivers but not accepted. 

I added a Radeon 9000 graphics card with 256MB, 1 VGA port and 1 DVI port.  It works in boot up only just like the onboard VGA.

In the display setup, the display settings show a resolution of 1920 by 1080 with Medium (16bit) color that will not change.  The ADVANCED tab is grayed out and the Troubleshoot tab is of no help.

I reloaded drivers and the system BIOS with no change.

I ran the DELL diagnostics with no problems found and scanned with House Calls and Malware finding nothing

Any ideas would be greatly appreciated