memory - How to stop Windows 8 from caching large files?

Edit

The video files I talk about were unrelated to LoL (game). They were separate files that I personally downloaded. Of the 8GB that was used then the game crashed, the game was using less than 500MB. Chrome was using 1GB. The system services was using less than 500MB and everything else I have running was less than 1GB. My average memory consumption is around 2.5GB - 3GB for all programs / games.

Edit

The 6GB being used was after I closed the game and all other apps out. When the game crashed all 8GB was being used (non in standby or free / not available to be used when needed) with 5GB of it being cached MKV video files that were not in standby/free. The game was able to crash with "out of memory" because I have my virtual memory (swap file) disabled (the problem was not the game being able to crash but why these large MKV video files were sitting on all of the memory pool forcing the game to crash).

TL;DR

Windows 8 was caching a ton of large MKV files as active memory (not standby). These MKVs were not open in any program and this was after several restarts without opening the MKVs. Using RAM MAP to release all "working sets" cleared all the MKVs from RAM cache and reduced my RAM usage from 6GB to 2GB.

How do I prevent this?

INTRO

I'm running Windows 8 64bit with 8 GBs of RAM.

I don't use a lot of programs. The only "heavy" programs I use is Chrome, League of Legends, and perhaps Malwarebytes. Not a whole lot.

Yet my game kept crashing with out of memory errors. I was getting really puzzled by this because I know I wasn't using 8GB of RAM with what I was doing.

So I look at task manager and adding most of the stuff in my head I get around 2GB used by resource monitor reports 6GB being used (with no active "heavy" programs). Really puzzled now.

Get more detailed with Ram Map program. It tells me that mapped files are using 4GB is not a bother to me if it's all in standby or ready to be released anytime. But it wasn't... all 4GB was active not in standby.

So I dug deeper and went to file lister and listed it by active memory and found the culprit...