So my PC is a Alienware X51 that I bought something like 8 years ago (jesus fuck christ has it really been that long?!)

Anyways, the machine has 8GB of ram. for some reason, these past few days it has decided to only use 4 of it. No clue why or how. But if I open up task manager I get this:

note the “cached” and “available”

What gives?