My right click menu has disappeared?

You probably have a bad context menu handler interfering with your right click menu.

First download ShellExView and run it.

http://www.nirsoft.net/utils/shexview.html

This will scan your computer for the shell extensions. Give it a few seconds to complete and then click on the the "Type" column to reorder the list by Type. Look for the context menu handlers.

Disable non-Microsoft context menu handlers one by one while checking to see if the right click menu reappears after rebooting.

You can save time by disabling several context menu handlers at once by selecting multiple lines before rebooting. This will help you narrow the list, make sure you re-enable the good handlers.