Windows 8 & 10
Hate the Modern UI of Windows 8. Keep Windows 8 and get back the missing START menu.
Project page on Sourceforge.
Note: Classic Shell has moved to it's own website so the information on sourceforge.net may not be the latest.
Advanced Tokens Manager
Microsoft imposes a limit on the number of times a copy of windows can be activated online or by phone. Advanced Tokens Manager is able to make a full backup of all activation data stored on your computer and allows the data to be restored without damage or modification of the activation system.
StartOnDesktop will enable the Desktop to be displayed at every logon instead of the Metro Start Screen of Windows 8.