I recently decided to upgrade my current Optiplex 790 MT and I'm not sure what I'm doing wrong. I currently have an MSI GTX 660 and wanted to upgrade to a MSI GTX 970. I also tried switching my power supply to a EVGA 600w for it. I'm not computer savvy so have been using YouTube videos as guides but despite that, my computer won't Post. An amber light blinks and 1 and 3 are highlighted. Reading a guide, I tested the power supply using the paper clip test and got it to spin. I also swapped the CMOS battery with a fresh one. I took out all but one of the RAM sticks and decided to revert everything back to see if the motherboard worked and it does. I'm super lost and don't know what to try. I appreciate anyone that could help or message. If there's anything you need like a picture of the insides or the exact parts, I'm more than willing to answer anything. Thank you to anyone reading.