Windows 7 Manager is an all-in-one utility that helps you optimize, tweak, repair and clean up Windows 7. It will increase your system speed, improve system security, tweak startup and shutdown speeds
...of Windows 10, more Windows 10, and some other stuff
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Windows Tweaker is a free Windows tweaking utility using which you can tweak your Windows 8/7/Vista/XP. It contains several tweaks grouped into 11 main categories and access to 38 Windows tools.
Tweaking.com - Advanced System Tweaker is a central hub for any kind of tweak or anything else that can be done via registry files, commands and vbscript files.
jv16 PowerTools is the ultimate registry cleaner and Windows tuneup utility suite. You need oil to keep a car engine running. You need jv16 PowerTools to keep Windows running.
Kingsoft PC Doctor Lite is a free bundle of system protection and maintenance utilities. It includes tools to clean and optimize your browser, operating system, registry, and data.
Ultimate Windows Customizer (UWC) is the first integrated freeware that offers you almost everything that can be customized in a Windows installation - well everything that matters, at least!