Programs can add extra options when you right click on a file or folder ( such as compress to zip )
Most of the time you can customise these from within the software itself. However some programs do not give you the choice, can leave behind options after uninstalling, or cause a delay before the menu appears.
I found 'tools' to edit context menus to poor, but luckily the options are easy to remove by editing HKEY_CLASSES_ROOT section of the registry.
For all files and folders
For drives in My Computer