Computer store lackey: Hi, li'l lady! Are youuuuu looking to buy a COM-PYOO-TARR?! We have these DELLS that-
Me: Yeah, no. Where's your memory? I've been up and down the aisles here like five times, and--
Lackey: Ohh, that's for UPGRADING! I'm sure you're looking for a shiny new LAPTOP, right? We've got three aisles of them right over--
Me: NO. Thanks. Have computer, need RAM. DDR, 400mhz, paired 1 gig sticks, s'il vous plait.
Lackey: Here's a whole bunch of DDR2!
Me: ...how nice for you. Can you show me what I ASKED FOR, PLEASE?
Lackey: Oh, DDR doesn't exist any more. You'll have to upgrade your motherboard. Can I show you our--
Me: I can kick your testicles through your sinuses.
Lackey: Oh you mean THIS DDR RAM?! Silly me, why didn't you say so? Yes, here's all three of our offerings.
Me: Wait, WHAT.
Lackey: Yeah, we had a clearance on those 1 gig sticks of DDR that I said we didn't ever carry so we're all sold out.
Me: So when do you restock?
Lackey: Oh, we're not. Everyone just uses DDR2 and Vista now, y'know.
Me: *twitch* Fine, I'll take a matched pair of 512's then, since they're still cheap and better than nothing.
Lackey: Are you sure you don't want to upgr- *oh god the eyes, the eyes are full of hate and death* YES OKAY HAVE A GOOD DAY MA'AM!
~~later, in the computer boudoir~~
Me: Hunh, the 512's I have in here are split out. Weird, I could have sworn I had a matched pair. Guess that's what age does to the memory, har har! Let's slap them together and stick the new pair in and see what happens!
Computer: LA LA LA LIFE IS GOOD LIFE IS HAPPY URK.
BSOD: I AM CRYPTIC!
Internets: Hey, if you force this sneaky rebuild of your virtual pagination file this can fix your problem!
Me: Woot! *fixes*
Computer: LA LA LA LIFE IS GOOD LIFE IS GACK.
BSOD: Totally different problem! FOOLED YOU!
Internets: Microsoft says to fix this by taking out the new RAM and forgetting about the whole thing.
Me: I refuse to accept this!
Internets: DO NOT DEFY THE WILL OF MICROSOFT!
Battle: *KATANAS CLASH*
~~many, many hours and driver updates and reboots later~~
Me: All right, all right, something is severely fuxxored here, I'll take out the new RAM.
Computer: All is back to normal! The status quo has been restored! Peace has returned to HURRK.
BSOD: WHAT A TWEEST!
Me: OH NOW WHAT THE FUCK.
Internets: ...don't look at me, dude.
Me: JESUS FUCKING WEPT, SERIOUSLY! THE ONLY THING THAT'S DIFFERENT IS THEY'RE IN PAIRED SLOTS NOW INSTEAD OF SPLIT OUT, WHICH DIDN'T EVEN MAKE FUCKING SENSE SINCE IT'S A PAIRED SET unless one of the slots is borked, I guess, fuck, I'll swap the chip back over... crap, I can't SEE under this desk, where's my flashlight... *click* hey, why are the slots colored alternately? It's almost like OH MY FUCKING GOD.
Cats: *wisely flee to other end of house*
So, long story short, new RAM is working just fine, and don't try to install new hardware in the dark, no matter how well you think you know your motherboard.