Basically the PC won't boot when I have all 4 sockets installed with RAM. Left 1 RAM on first socket, PC booted successfully with a little overclocking error, saying I need more than 1GB to run stable system. Tried inserting another one in 2nd slot, also launched. Although, whenever I have another in slot 3 or 4 or even both, PC doesn't boot. Tried inserting to 1 and 3, it also didn't boot.
Here's full story if you're interested
I've shut down the PC, ripped off front panel of the case and got little arachnid out that I spotted earlier that morning. I didn't even bother putting the panel back in, plugged everything in and all of the sudden PC wouldn't boot. No beeps, no signal to monitor etc. The creature couldn't have caused that, I'm certain, as at worst it had its web set up around HDD section and front of the case. On top of that that computer was running all fine prior to me turning it off. My PC has also been running on quite high tempts when under load lately, but that's now fixed with little fan recalibration and cleanliness intervention. Did full reassembly meanwhile having this problem, thinking could've loosen some connections.
Mate suggested might've had something to do with static discharge or similar. However I am aware of static and generally am careful with it when comes to electronics. But that still stands as a possibility. Also all 4 RAM sticks seem to work fine.
CPU Intel Core 2 Quad Q6600 @2.40Ghz
MOBO Asus P5B-V
Apacer's Desktop Memory DDR2-667 and the pqi ddr2 800u is a DDR2-800
so they are not the same brand and type ...so they are not compatible each other
install just a dual channel kit ...for example , use only the pqi ddr2 800u kit or only the Apacer's DDR2-667 kit
Pardon my rudeness, but are you certain they are that incompatible with each other? I'm rather a rookie in this, so I could be missing something. However they used to work fine before, so how come exactly now? In case of missing something in specifications I took screenshots from HWiNFO32. Hope it isn't missing anything.
Also while swapping RAM sticks this morning I noticed that system works fine with 1GB stick of APACER, while having 1GB PQI gives an overclocking error on POST. When was done and set the PQI cards back in 1-2 slots, at first the system didn't boot, yet worked fine yesterday. A mere restart fixed it, the thing gave a beep, although it froze on boot logo. Couldn't enter bios either, so I did around 4 restarts which gave no changes, thing was still freezing. Powered it down and tried lightly pushing the RAM sticks in, thinking they might be loose, but they sure didn't feel that loose? Upon powering back up it booted and passed POST. Thanks for your time!
Guessing ASUS P5B-V doesen't allow you to tangle with these in BIOS. Although I was able to change frequencies. The thing was on set on AUTO, so I switched to 800, did a reboot and it booted successfully. Tried switching back to AUTO and it booted without an error as well. Weird? It indeed is, at least for a newbie like me.
Also a note; before I tried inserting sticks in different orders before, like, PQI slot-1 + APACER slot-2 /reverse, just PQI/APACER slots 1-2, system booted, though I could not make the system boot whenever something was in slot 3, 4 or both.
So the problem is solved. Cheers to badboyrog2 and whoever else brought interest!