TrendMicro HijackThis may sound like the name of a piece of malware. But, it is actually a freeware utility from a respected security software firm that scans your Windows computer to find settings that may have been changed by spyware, malware or other unwanted programs. Note that HijackThis is a diagnostic tool that does require a bit of expertise to interpret.

It works on versions of Windows ranging from Windows 98 to Windows Vista.