While Microsoft Security Essentials does a fairly good job of protecting your computer from PC-threats, when accompanied with free proactive protection like SafenSoft SysWatch Personal the result is a fortified PC without the need of any paid security software.
SafenSoft SysWatch protection system preserves the integrity of your operating system with all its components and applications as installed at the original build. This protection system works by controlling how applications behave by keeping a record of your “known-good” computer state, preventing hacker attacks and malicious software from activating. Because SysWatch Personal does not need to identify individual threats in order to block them, it doesn’t need all those signature updates required by traditional security software to provide reliable protection. Featuring three core functionality of controlling the application launch process, application activity process and the self-protection system the addon offers fast and reliable protection even against unknown threats.
Unknown applications are launched and activated only in a secure sand-boxed environment mode and authorized users can use the "Install Mode" to permanently store the new unknown application and changes made by it. SafenSoft SysWatch also features the handy digital certificate trust module which automatically unblocks installation of known white-listed applications having a valid digital signature (this seems to be a paid upgrade/other SafenSoft product feature as the same is not visible in free version but was infact shown in demo video). Please do keep in mind that SafenSoft SysWatch Personal do not fight the consequences of infection, but prevents it from happening - hence the pro-active defense for your computer.