Get a faster PC. Also, there was a test version of Mach3 that let you manipulate the toolpath display while the machine was running with no ill effects. You may have seen that version.
But I think the faster PC may be all you need, preferably a dual core or better. I've never run a machine on it, but on this machine, a dual core, I can switch screens very quickly, but on my machine PC, it takes about a full second to switch screens.