Yes, I'm using the Free version also.
Thought about buying the paid one, but:
*after giving the paid ones a try (simply download it), it will bombard you with firewall requests, you might get lazy and allow something that's really malicious (the free one does only ask for non-windows services, which make up most cases and are related to 3rd-party software and or malware)
*not sure whether I have to buy a new key / contact the support once I reset the PC (I don't recall that sentence: "Re-registration is required after upgrade or re-installation onto a different media (backup restoration causes the media virtually changed sometimes). The registration code change confirms the re-registration was required for the reasons above.")
Instead:
*use TCPView when you're paranoid, check out svchost.exe, explorer.exe (definitely malicious, haven't seen it in legit function calling outbound), msbuild.exe,...
*check AutoRuns for suspicious entries regularly
*process hollowing should be detected and prevented by a decent AV