A Sandra report and info on your interface are needed before anyone can offer better advice. I believe that you really need to try Windows 10 with recent versions of PT. As much as I liked Win7 better, once I bit the bullet and got used to 10, it seems to me to be a leaner OS and I have far fewer errors than I had back on Windows 7(assuming 64 bit in all cases).
Beyond hardware info, are you trying to track with several amp sim plugins? Those are notorious cpu hogs so freeze or commit to reduce load on the computer. Some other plugins that are known to drag a system down include Ozone and Melodyne(I have to max the buffer when running those). Also, high sample rates(88.2 or 96K) double the load, so you might find 44.1 or 48K just fine for most commercial music releases(I certainly do).
Last tidbit; your i7 960 rig is fairly ancient in terms of computer hardware. I ran a 980X/x58 for a while and my semi-ancient 3930K/X79 rig runs circles around it
