Sounds like you need to research different port scanning techniques and better ways to find exploits. Try limiting your port scans to only a few different ports at the same time. Pick some popular ones. And as for finding exploits... there's no real quick and dirty way that's super effective. Just gotta look through all the major websites out there that list them.
As for unpatched Windows 7 machines, I don't believe there are any exploits out there that can cause remote code execution from outside the machine. The last one that I know of was MS07-something. Remote code executions under Windows 7 probably have to be executed from a booby trapped file.