Computer keeps freezing for long periods of time

I have two issues that need to be addressed and I think that they are connected in some way. The first problem is that my computer has begun freezing for long periods of time when I load things. It most recently happened when I tried to load a new page on DeviantArt, but it has happened when doing things as simple as opening a new tab in google chrome or trying to alt+tab to skype. The freeze either lasts a few minutes or much longer. When it lasts longer then 5 or so minutes I decide to force shutdown my computer.
The second issue that I am encountering is that task managers claims I am using 100% of my disk space sometimes when I have very few things open. Usually the culprit is System or Antimalware Executable, two services I can't turn off without shutting down my computer or making it unstable, but sometimes it says I am using 100% of my disk space when the app/service using the most disk space is using a measly 0.1 gb/s or lower. I have tried multiple solutions to this problem, including turning off Windows 8 autoupdates and allocating more memory to certain things, and disabling Super fetch and Windows search.

These are the specs on my Asus laptop:


Something I haven't mentioned is that I dual-boot Ubuntu, but I haven't used it in some time. After upgrading to Windows 8.1 the BIOS reverted back to its default so I just kind of forgot about it, but I never reallocated the space that I had initially allocated to Ubunutu.

The freezing issue started a while back, and I haven't found any viruses on the computer nor can I find any programs through the control panel that I think might be causing the issue. The 100% disk usage issue has, as far as I know, been a problem since I first got the laptop. I'm not sure if that in conjunction with something else is causing my laptop to freeze.