From HowToGeek

If you use the excellent TortoiseSVN application to manage your Subversion source control system, you might have wondered why the shell extension shows up on the desktop context menu when you won't ever have source control on your desktop folder.

Note: If you do have your source controlled folders on your desktop, you should seriously think about organizing your files better =).

Just for those that might be confused, I'm talking about disabling this menu on the desktop or folder background context menu. Note that this will remove the menu from the folder background pane as well, so in order to checkout or import files you will have to right-click on a folder.

We can disable this menu item while still letting the right-click menu work fine on the folder itself.

Disable the Menu Item

Open up regedit.exe through the start menu search or run box, and then browse down to the following key:

HKEY_CLASSES_ROOT\Directory\Background\shellex\ContextMenuHandlers\TortoiseSVN

Find the (Default) key on the right-hand side, and then change the value to have at least one - at the front of it.

Now you shouldn't see the menu item on the context menu anymore:

Hopefully somebody will find this useful!