There is no display on the moniter when the computer boots! I've. Tried unplugging the gpu and start with the onboard vga display but still no display! The computer runs but the display is not working! Is something wrong with the motherboard??? Please help!

Any display during the POST? IF so, try booting to Windows safe mode by hitting F8 priot to Windows booting. IF not, have you tried a different display just to rule out the issue.

If it seems to boot, but you have no display, then HOW do you know it booted successfully? Also, have you verified that the display isn't broken? If a laptop, what if you boot with external keyboard/mouse/monitor, and the top closed? Does it show anything on the external display?

Its a desktop! and I've tried in my tv also and absolutely the screen is blank! The pc start with a sound and the led flickers! By that i can guess it is running!
tell me if i am wrong! Is it a problem with the motherboard?