HijackThis is free and open-source tool for Microsoft Windows that tries to detect malware/adware by comparing a Windows system with a list of files that are normally found on a uninfected Windows system.
It is used to find registration of 3rd party tools/software in Windows system and usually used to find and de-register adware/malware.
Development stopped after purchasing project by Trend Micro company.
They still provide free version but most annoying: it doesn't handle paths on x64. Program can detect registration but usually shown that file missing because program doesn't adopted to WOW64 Windows subsystem.
Any alternatives to HijackThis?