Memory troubleshoot help and voltage question

I think I've been stricken with a bad stick of RAM in a system i recently bought. All parts check out except one of the sticks, but about 9.5 out of 10 times (it still does hang post...well POST)

Basically 9 out of 10 times, turn it on, and it just stays at a dark screen, doing one long continuous beep, stopping, then doing it again.

.5 out of the remain one times, it does not successfully make it to windows and/or sustains operation shortly after loading windows.

the remain .5 times though, no problem. No lag, operation is flawless, except it has twice frozen up (and then rebooted to that long continuous beep). I had it up for 24 hours of basically nonstop gaming, had a LAN party last night, but today, upon starting, it froze then went to the beep again.

1 stick out has yet to produce any beeping (thus i think i have a bad stick), but why isn't it constant then?

Mobo : Asus P5N-D
CPU - Core 2 Quad Q9450 2.2 Ghz
Memory : 2 x 2GB Corsair 800 Mhz PC26400
Windows Vista Home Premium 64 Bit
(anything else needed to be listed?)

My voltage question is that, I have found the "same" stick on Newegg, all specs match, except voltage. I have 1.8v sticks, newegg has 1.9. Is that of any significance if i bought a single stick to replace this one?

1.8 v is what is written on the stick.

One stick test though.. .


Stick A (Alone) : Boots normally

Stick B (Alone) : Never gets past bios beeps

Sticks together : like i said .5 out of 10 for successful boot through to windows running without immediate hang up

I understand what you are saying about testing each one. but 1 doesn't even give you a chance to boot into any tools. Taking a stick out however, gives me the chance to modify settings in hopes of fixxing it, and thus to repair it. But in that state, i obviously can't test the other stick that is "bad".