Looking for general help on a PC I built 8 months ago

Hello there Tek Syndicate! I very much doubt anybody remembers me, but I was active in November-December time of last year and, with your help, I managed to build my own PC. That's great, but I'm recently encountering a few issues, but certainly not serious ones. Regardless, I'd like to ask for your help once again. 


Firstly, we have a case of 4GB of my RAM not showing up. I was looking at Task Manager generally the other day, and I saw something strange, considering I had very little running. My Memory Usage was at about 95%, even though I only had a few tabs of the internet open. This one tab is all I have open currently on my entire PC, and look at the memory usage: http://s29.postimg.org/hs94dftjb/RAM.jpg

A few days later, I looked at this, and this is what I found, even though I stuck 8GB of RAM into my PC when I built it: 


Why are only 4096MB showing up? 


I was also wondering what a safe level of GPU setting would be? I haven't changed any settings since release, and I haven't really even looked at the programs I downloaded when I installed the disks, but they're interesting me now that I've looked at them. I'd like to see how powerful I can safely make my Graphics card. Here's my PC Specs:

CPU: AMD FX-8320

Motherboard: Asus M5A97 EVO R2.0

RAM: (Should be 8GB, but only 4GB are currently showing up. See previous question).

GPU: MSI R9 280x

Lots of spare storage, and I have Windows 7 64Bit Operating System. 

http://s10.postimg.org/xrpfqkevt/MSI_Afterburner.jpg : Those are my current settings on MSI Afterburner, do you think I could increase them at all? I am looking to try and download some ENBs on Skyrim, so I need my system to be running at maximum proficiency. 


How does MSI Gamingapp work? I only looked at it recently, and I think I understand. 

OC Mode is maximum performance, Gaming Mode is steady-high, Silent is lower-quiet and cooldown is lower-less heat. However, when would I use Gaming Mode over OC Mode? 


I'm just generally wondering about how to go about using it, any tips?


I'll combine the last two questions into one.

The penultimate question is: Is there any way to search for the programs that were downloaded with the discs that I installed when I recieved them with the component itself? I've heard that there are many MSI things such as recorders and things that are installed, but the only programs that I can find installed are these, and I have no idea how to use the AMD Catalyst manager one. Are default settings normally right? 



Finally, one last question. It's about a specific game, Chivalry: Medieval Warfare. It's not about the game itself, but how it runs. It's mainly online and has many people (Sometimes 30+) playing at one time, sometimes on one screen. However, this does not explain my frame drops. It could well be my internet, but I can run games like Skyrim, Fallout NV, Shadow Warrior, etc on Maximum settings, so why am I getting drops on Chivalry? Has anyone got any ideas? I know that it's just me and it's just on that game, so it's not server side. Any ideas, or is that too vague?


Thanks for any help!


For your memory issue I'm assuming you have 2 x 4GB. 

I'd take them both out then refit them.  

Assuming that doesn't change anything you can try just one at a time to make sure they both work. 

If none of that helps you can run the Windows memory test.