PC wont boot up with more than 1 stick of RAM

mobo: asus p5b 
CPU: intel c2d e4600
GPU: R9 270 

So i used to have 4 gb of ram and then my pc broke. i take out 1 stick. all works. than the same thing i takeout 1 more and it works. It happened again and now i am stuck with 1gb. 

Strange thing is windows say there are no errors on any of the modules and it works in any slot on the motherboard. 

I am thinking it could be PSU. 
And yes everything is plugged in correctly

May not be mobo ... more likely your ram sticks are failing

test 1 stick at a time with memtest to see if they are bad

just checked turns out one of the capacitors bulged