How do I clean up the right-click context menu in Windows explorer?

You can use ShellExView to disable context menu addons.

You have to edit your registry, it's easiest do do this for the context menu of directories:

• Run regedit
• Navigate to HKEY_CLASSES_ROOT\Directory\shell
• Remove the keys that correspond to the unwanted commands

Each filetype (file extension) has its own additional commands which you can find under HKEY_CLASSES_ROOT\Directory\.EXT

If you want to remove a specific menu entry, it might be easier to just search for the context menu string in the registry.