Try upgrading to 10c, also make sure your media is not on the same drive as your OS. I have 6 drives in my system and have two for project files, 2 for rendering to, One SSD for main system drive and one for storage.
The only thought with your processor is that it is not even over 2gh….that may have something to do with it as well. I am using an AMD 6 core that runs at 3.2 Ghz..and a lot of the other i7’s are about 2.5Ghz or more as well.
Again with what John said…you may be using a CODEC like AVCHD that may be more difficult to work with..
Good luck!
Scott Francis
Mind’s Eye Audio/Video Productions