When you right click on a folder or file with the Explorer, a list of options is available.
As more applications get installed, this list may get too large for you.

To remove items from the list:

Note the text of the item you want to remove

Start Regedit

Go to the following sections in the Registry and delete the subkey with the string you noted in Step 1.

HKEY_CLASSES_ROOT\Folder\shell
HKEY_CLASSES_ROOT\file
HKEY_CLASSES_ROOT\Directory\shell