Crashes when gaming or streaming while a high amount of memory is used

Windows 7 Ultimate 64-bit Retail installed in my main 80GB Intel SSD roughly 2 years ago.

All the hardware (image below) is fairly new except the hard drives which I am unsure of and have been reusing from build to build. I have 2 pairs of G.Skill RAM in different sizes, but same specs (2x2GB & 2x4GB). Crashes have been starting after installation of the 2X4GB RAM although I have been doing other tweaks to the computer from then on. Some registry stuff might have been accidentally deleted as well.

My main problem is the blue screen crashes.

So far, I've addressed my Realtek PCI-E reader's driver update as there was a problem relating to it and some video encoder.

My Windows Media Player also freezes after watching ~10-20 minutes of a video and then switching over to another. I think I read somewhere this had to do with video codecs (CCCP) installed on my computer, but if someone thinks I'm incorrect please help me with a fix.

Thanks!