Failed upgrading optiplex 790 mt

I put a new power supply in my Dell optiplex 790 Mt, and a new graphics card. I had it up and running with the factory i5 processor, and I upgraded to 12 gbs of RAM 2x2gb 2x4gb. Today I tried to upgrade my processor to an i7 2600, and I tried to swap out a 2 gb stick of RAM for a 4 to make 14 gb.

After I put my processor and new ram stick in, I went to boot up the PC. All the parts spun, and it booted to a yellow light (should be blue) and would not give my PC picture. I start trying to reverse the process, ended up putting the i5 back in, still yellow light and no picture to the monitor. I went back to the original ram, still yellow light and no picture to monitor.

For my picture I'm using dvi-d cable from my gpu to the monitor. This is all very frustrating and I wont have the money to upgrade or fix this for a while.

What am I doing wrong? What should I try doing? Thanks for any help