Dell c640 The VGA display was disabled now after start-up screen I can not see my desktop - screen is BLANK GREY. How can I re-enable so I can see log on screen again after initial WinXp screen. Thank you!

Fist open cpu cabinet cover then pull cmos cell from motherboard for 10 minutes then put it back then all settings goes defaults.The when you power up the computer press F8 key 5 to 6 times then you can see safe mode and other menu enter in enable vga mode then go to display property and change screen resolution to 1024*768 then apply also press windows key +R key so you can see run type in run "chkdsk /r" then press enter then press "y" then restart then it will fix and recover error of windows and harddrive.If you are not able to enter in enable vga mode then try to enter in "safe mode" then run "chkdsk /r" command with above method then if still same then need to repair windows with windows disk.Let me know if you need further assistance.Thanks for using FixYa.

some bios settings disables the add on video cards. to enable them go to bios setting by pressing DEL or F12 while power on your system. (u will see that a message appears "press ----- Key to enter bios settings). after entering bios setting u will see onboard VGA enable/disable. u have to disable onboard VGA in order to get the display thruogh VGA card.

Step 1. Reboot the machine and during boot up continuously press F8 to enter Safe Mode

Step 2. When you computer boots into Windows, enable your VGA adapter if it is not already.

My guess is that the Display driver doesn't support the resolution of the TV, once it loads, after the Dell Splash screen, it goes blank

You need to activate the output. Left click somewhere on the desktop screen to bring up the display menu and then click on <properties> at the bottom and then click on settings. You should see the 2nd display. Enable it and duplicate the desktop (not extend) to the output. That is the generic procedure- yours may be a little different.
Let me know if that doesn't do it.
JC

hold f8 and select use last known settings that worked.

Sometimes after changing BIOS settings the computer will not start or will possibly give error messages similar to yours. I have at times had to remove the power source, remove the motherboard battery, and set the motherboard back to factory default settings. You also stated that you installed a new motherboard. That could also be a potential problem. If the computer has never started with the new motherboard, the new board may be defective.

enable your onboard graphics and plug your monitor into the onboard. start up your pc and install any needed drivers for the secondary graphics card. right click on your desktop and go to your display properties you should see a faded out screen that has a 2 and a lit screen that has a 1 right click on the faded screen and check enabled then move your monitor cable over to the new vid card right click on the lit 1 and disable it making 2 your primary.

in bios settings there is a option enable or disable onboard display card check , one more option is there press F8 key when you are restarting the system some options is come their select enable vga mode

If there is no display on your TV, HDTV, or Projector, please make sure that all of your connections are set up properly and that you have enabled the display in the Catalyst Control Center. The connectors that you will be using would be Svideo for TVOUT, DVI-to-HDTV (Component video), VGA-to-HDTV (Component video) for HDTV, and DVI, VGA, or Svideo for the projector.
Here are the steps to properly setup and enable TV, HDTV, or Projector:

• Turn off your PC and your TV, HDTV, or Projector.
• Ensure that your card was installed correctly, as per the Getting Started Guide.
• Determine if your TV, HDTV, or Projector has a S-Video (for TV), YPbPr for (HDTV), or VGA/DVI for Projector.
• Looking at the back of your PC, locate the needed connector or the supplied adapter cable; attach one end of the cable to your graphics card and the other to your second display.
• Turn on your second display then your PC.

If you are connecting an HDTV to your video card, please Click here for detailed instructions on how to set it up correctly.
Starting Windows with TV or Projector Display Enabled The TV screen may become scrambled during the initial Windows® logo display. This is only a temporary effect and your screen will be restored within a few seconds. During start up, your RADEON will go through a sequence of mode settings, during which your TV display will remain blank. This process takes only a few seconds and helps program the TV display.

• To enable the second Display
• Right-click anywhere on your desktop
• Click Catalyst Control center
• View
• Advanced view
• Display manager
• Detect Displays
• You should have the second display picture under “Attached displays currently disabled
• Drag it to the box on top of it
• Apply
• OK

If for any reason the second display does not get detected, please do the following:

• Open the CATALYST CONTROL CENTER
• Go to Display options
• Check “Force TV detection” *
• Apply
• OK

* Force TV: Allows you to force TV detection if the ATI driver does not automatically detect TV-out connected to the graphics accelerator.
Possible issues:

• Computer monitor loses sync when TV OUT feature is enabled
• Text appears blurry on TV
• TV OUT is black and white with a PAL-M or PAL-N television
• TV OUT is enabled randomly at boot, even with no TV attached
• Image on television is cropped using Overlay Theater Mode
• With Theater Mode-Overlay enabled in Clone Mode and selecting the "Swap Device" option results in the system restarting.
• Corruption may be noticed on an HDTV after setting the resolution to 1080i and enabling Overlay Theater Mode.
• When using an HDTV in extended desktop with theater mode enabled, the video does not display

In case the users display does not natively support HDTV display timings in the EDID, you can add standard HDTV modes so that the usual HDTV resolutions (720p, 1080i, 1080p) are listed in the Display Manager resolutions. You can also create custom HDTV timings to solve any kind of over-scan options (for cases when the windows desktop appears to not fit on the HDTV screen, and the outside boarder is cut off).
For more information on connecting your second display to your Video card, including supported output device combinations, please refer to your user’s manual.