maybe is the PSU, but your PSU is still good its just probly because you dont have enough Watts to power all of the components when you add your two other sticks of ram. what is your PSW wattage ?
Ill give as much information as I can. I have a Dell 530 Desktop Quad core with 2 extra gigs of ram I added by myself as well as an 8800 GT I added.
I turned it off for the first time in a good week or 2 and when I tried to turn it back on it would try and the fans would jerk and continue to do so but it would never get full power.
I took out 2 of the ram sticks, turned it back on an it worked fine. Then I put both back in turned it on and it worked fine again. Well after 2 days I shut it off again and had the same problem when I attempted to turn it on.
Again after I took 2 of the sticks out it turned on, this time though it would not turn on with either or both of the sticks in. I tried every combination possible but the only way I could get it to turn is with both ram sticks out.
PS this computers obviously a few years old and had everything "aftermarket" since the day I got it and ran flawlessly since that time until now.
Thanks in advance for help