1080p videos suddenly lagging?

[mofudder]

I was using MPC for a whole season of friends but all of a sudden the videos located in my HDD began lagging really badly, but this only started after like 15 episodes?? Now sometimes it runs but only if I sign out like 5 times.
This also happens on VLC. I'm currently using ~11% of my CPU and ~50% of my memory and it still lags.
What can I do??

I have an Asus S550CB
i7-3537U @ 2.00GHz
8GB ram
Windows 10

Thanks a lot!

 

[Reynod]

Defrag the drive and uninstall then reinstall VLC. Also run a virus and malware check, then use process explorer to see if some background system process is not chewing up tons of cpu resources.