|"I have tested my NVidia 8600 GT and Monitor on another pc and it works absolutely fine."|
So there's nothing wrong with the original card.
"...borrowed a 9800GT 512 MB video card, installed on my pc every thing worked fine ..."
So there's nothing wrong with your mboard or the PCI-E X16 slot circuits.
"I even upgraded the PSU and it did not help."
That was probably not necessary.
"The pc boots normally when the monitor is connected to the onBoard VGA graphics device."
Is that with the original graphics card or the 9800GT card removed, or with it still installed?
Most bioses automatically disable the onboard video when you install a video card in the PCI-E slot, but I have learned through experience that doesn't always apply to recent mboards with certain main chipsets - your mboard is recent and has a recent main chipset.
If the onboard video works when a PCI-E X16 card is installed, if you get no video at all from the PCI-EX 16 card, you need to change a setting in the bios Setup.
Apparently, for your mboard, most of the detailed info about your bios Setup settings is NOT in the manuals for the mboard, but that info is here:
Boot settings glossary
- you press F2 repeatedly while booting early in the boot to get into the bios Setup.
E.g. right after the mboard beeps once.
Advanced > Video Configuration
Boot Display Device - DVI + VGA, or VGA + LVDS
Designates the Primary graphics device.
- default not stated
That's oddball labelling - I have no idea what the difference is.
Whatever it is set to, set it to the other choice.
Also there is....
DVMT Mode - DVMT, Fixed, Both
- default not stated
It's probably best left set to whatever it is already set to, if it's set to a default setting.
If you're not sure whether that's set to the default, load bios defaults (see below).
For more info about DVMT mode
"updated the bios to the latest version."
That doesn't make any sense at all if the original card worked fine previously with whatever bios version the mboard had. It is extremely rare for bioses to get corrupted spontaneously. Flashing the bios is NOT a cure-all!
Flashing the bios often DOES NOT automatically load the bios defaults that go along with the bios version. If you flashed to a different bios version, if the bios defaults for that version were NOT loaded, then the changed bios version and any settings you make in Setup may NOT work correctly.
To MAKE SURE the bios defaults have been loaded, go into the bios Setup and load defaults.
In your case - select
Exit - Save Optimal Defaults
- Exit Saving Changes, or press F10, answer yes.
If the onboard video works when a PCI-E X16 card is installed, if you get no video at all from the PCI-EX 16 card, see the info above.
Standby and Hibernate will often NOT work correctly until AFTER the main chipset drivers have been loaded.
If you're not sure whether they have been loaded, go here and download them, and load them: