Asrock Extreme3 870: Post Code Error "D3"

So, I'm in the initialization phase of testing out my build, and everything's working, but my motherboard, an Asrock Extreme 3 870 is giving me 3 consecutive beeps at a time with the code number, D3, popping up. After looking it up in the manual, it says:

"D3 - If memory sizing module not executed, start memory refresh and do memory sizing in Bootblock code. Do additional chipset initialization. Re-enable CACHE. Verify that flat mode is enabled."

Since this is my first build, I am both extremely confused and nervous. I don't know what to do in order to figure out the problem and I keep thinking if I mess around with it, I'm gonna blow something up. All I can guess is it has something to do with the RAM, but I'm not entirely sure. Is there any way to test this without just RMA'ing everything?

Possible mishaps I made:
1) I think there may be one motherboard standoff not being used underneath the motherboard, if that could be a problem.
2)When I put on the heatsink, I screwed up the orientation, and pulled it off (along with some of the thermal paste). I put it back on correctly in the next minute, but I didn't know if thermal paste would count as an issue here.
3)My hard drive was a cheap recertified model. I don't know if that's part of the memory module or not.
4)I'm using a very old video card for the time being, until my 560 Ti comes this weekend. I honestly don't know what model it is; it doesn't say, but it looks like an old Geforce model.

*I put this in motherboards and memory board because I thought the main problem is either the motherboard or the memory, so yeah.