Malware authors use a variety of underhanded ways of trying to infect your PC, notably using scripts including Visual Basic Scripting (.VBS), Java Script (.JS) and Windows Scripting (.WSH). AnalogX Script Defender is a free, simple way to get help thwarting them. Install the program, and then whenever one of those scripts tries to run on your PC, a warning pops up, telling you that a script is about to run, and asking you whether you wan to let it proceed. To stop the script, tell Script Defender to abort. If you're familiar with the script, and know it's safe, let it proceed.
You can tell Script Defender to stop other scripting types by entering the extension into the program, which will then stop that extension from running as well. Script Defender by itself won't keep your PC safe from all harm, but it's a nice addition to those concerned about safety--and these days, that should be everyone.