RAM upgrade causing issues

Here’s my current RAM setup (slots 1 and 3):
Kingston Hyper X 2x2GB DDR3
Max Bandwidth: PC3-10600 (667 MHz)
Voltage: 1.5V
Motherboard has 4 slots total
OS: Windows 7 64-bit

I added these extra sticks (slots 2 and 4):
Kingston 2x2GB DDR3
Max Bandwidth: PC3-8500 (533 MHz)
Voltage: 1.5V

The PC recognized everything right away, and honestly, the performance boost felt great. But now, things start acting glitchy every time I boot up. First, my audio driver went missing—restarted, fixed. Then the system fonts changed—another restart, back to normal. Next time, Firefox kept throwing errors until I rebooted again. I’ve scanned for viruses and everything looks clean. Is it possible these RAM sticks aren't compatible enough and are causing these hiccups? I'm almost afraid to turn the computer off because I never know what surprise is waiting for me, whether it's right at startup or a few hours into work.

Is it possible that my RAM sticks aren't compatible with each other and are causing these issues? I've actually been afraid to shut down my PC because I'm worried about another surprise—sometimes it happens right at bootup, and other times it hits me after a few hours of work.

Absolutely. Also, what was the reasoning behind that specific slot configuration? Typically, you want those sticks placed side-by-side. There really wasn't any need to space them out like that.

My PC ended up with the memory sticks in slots 1 and 3, which left 2 and 4 wide open.
I could try switching them to 1 and 2, or maybe 3 and 4... is there any way to optimize this?

Look, just put the modules into the slots that match the color—that's how you actually get dual channel working. Don't just shove them in wherever you feel like it. You need identical modules in each channel if you want this thing to actually run right.

I honestly have no clue how the guys over at the repair shop managed to wire it up that way..

Since Channel A usually takes slots 1 and 3 while Channel B covers 2 and 4, you probably got it right. Just give me the motherboard model—or maybe just check the manual yourself to be absolutely sure.
Like Benjamin King2 mentioned, the slots for the same channel are the ones with matching colors.

Slots 1 and 3 (where the old RAM is) are gray, while 2 and 4 have the new blue ones.
The motherboard is an ASRock P55 Pro/USB3..

When everything else goes south, just read the damn manual... specifically page 18:

)
2.5 Installing Your Memory Modules (DIMM)
This motherboard features four 240-pin DDR3 (Double Data Rate 3) DIMM slots,
supporting Dual Channel Memory Technology. To get that dual channel setup working,
you've gotta use an identical pair (same brand, speed, capacity, and chip type)
in the matching colored slots. Basically, to trigger that Dual Channel magic,
pop an identical DDR3 DIMM pair into the Dual Channel slots (DDR3_A1 and DDR3_B1;
those white ones; check p.12 No.6).
You can also pack all four slots with DDR3 DIMMs for a full dual-channel setup, but make sure they're all identical across the board.

Check out the Dual Channel Memory Configuration Table below.

Looks like all four have to be twins... though it feels like they're just being extra picky. They don't actually say it won't work if they aren't!

Nathan Carter67 said:Slots 1 and 3 (where the old RAM is) are gray, while 2 and 4 have the new blue ones.
The motherboard is an ASRock P55 Pro/USB3..

Look, just try jumping into the BIOS and manually forcing the clock down to 533 MHz. If that doesn't do the trick, then you're probably looking at a compatibility issue—meaning you likely need identical modules that actually match what's listed in that manual Michael Jackson10 linked earlier.

I don't think that's going to fix his problem, because all four modules really need to be identical, and he probably should have been more careful about what he was picking up in the first place. It honestly feels like a lifetime ago, back during the old Pentium III and IV days, when you could actually get away with mixing things up—like throwing in one 266 MHz chip, a 300 MHz, and a 400 MHz from a completely different manufacturer and having the whole system just work. But those days are long gone, and modern hardware just doesn't play by those rules anymore.

Here’s what my BIOS shows regarding the memory:

Total Memory: 8192 MB
Dual channel memory mode

DDR3 - A2: 2048/533 mhz DDR3 - 1060
DDR3 - A1: 2048/533 mhz DDR3 - 1060
DDR3 - B2: 2048/533 mhz DDR3 - 1060
DDR3 - B1: 2048/533 mhz DDR3 - 1060

That section is greyed out, so I can't change any settings. Everything looks fine according to this, right?

Look, it’s fine—but if everything runs perfectly with the old memory stick and starts acting up once you swap in the new one, then you're basically stuck having to hunt down an identical match. Just my two cents, but yeah, that's how it goes.

Every single technician at these tech startups tried to talk me into swapping out my RAM to stabilize the system, even though they could clearly see it sitting right there in the BIOS.

The issue was that the original stick was 1600 MHz with 11-11-11-28 timings—specifically DDR3L running at 1.35v—but I had gone out and bought standard DDR3 at 1.5v. (Even now, AIDA64 keeps reporting it as standard DDR3 1.5v instead of the actual DDR3L 1.35v I'm using)

Anyway, I took it back to Best Buy, swapped it out, and everything's working perfectly now.

So, after cycling the power on my PC a few times every day, everything suddenly started working perfectly. It’s been running smoothly for a week now—no issues starting up, idling, or shutting down. The RAM is being recognized correctly, too, and the whole system feels snappier. Who knows? Maybe the computer just needed some time to settle in.