The Screen not coming up.

I have Dell Rev A02 motherboard. Was working before. Wanted to upgrade the RAM, I had to check the type first. After checking , I put back the memory stick and power up. The fan was working, the board led was on and the CD Drive could open and close, the screen was no longer coming up. There is only one jumper with three pins. I removed and interchangedry the jumper on the pin. The screen came up and boot to set up.after clicking F10, it asked me to shut down and then put the jumper back to its original place. Since then the screen has not been coming up. I testd the CPU and the memory stuck in another motherboard, they were working. Kindly help