Since you have different ram modules, did you check the specs. Further, when you fully populated all ram slots, it definitely demands tighter timing control and that maybe your problem. You really introduced two possible sources of problems, timing and different specs which include timing. use the pgm. called Speccy and note the difference of ram. If HP offers to be able control ram setting, do so. BUT!!! HP hardly allows that to be done, its pretty much "locked-in" as in using auto-setting by default, but check the bios area. You best bet to control this issue is to have all ram be the exact same.
I recently have upgraded an HP G7-1150US laptop from the stock 4GB of RAM to 6GB and then 8GB. This is a 1st generation Core i3 laptop that can take up to 8GB of DDR3 RAM. I upgraded the BIOS to the latest version on the HP website.
The RAM I used is from systems that were upgraded to larger capacities. As this computer is a cast off to run a security camera system, I didn't feel like buying RAM just for it so I re-used other cast off RAM.
Anytime I used RAM from a newer generation of laptop, the computer had memory issues. The first try didn't even get it to boot. It would post but get a BSOD on start. The next RAM booted the system but ha a BSOD within hours or days depending on how it felt. Since it wasn't doing this before I upgraded the RAM, I went back to 4GB until I got ahold of 8GB from a same generation system. The older 8GB set worked jut fine.
I know the RAM from the newer systems is good as they ran great. Is there some incompatibility between RAM types on the earlier generation Core I series chipsets?