First navigate to Notepad.exe and note (or copy to clipboard from a shortcut tab) the exact pathname of Notepad.exe (eg C:/Windows/Notepad.exe). (Use Pathcopy utility if you have it.)
As always, backup your registry before making any changes.
Now open Windows/Regedit.exe (Run...regedit).
Expand the Hkey /Classes/Root folder by clicking the + sign. Highlight the * folder (near the top of the list). Click Registry at the top and click Export Registry File. You will get a dialogue box---give the file a name, say Shell, and tell the computer where you want the file exported to. I suggest your C folder. What you are doing here is sending a copy of this part of your registry to another place on the computer where it will appear as a .reg file--in this case C:/Shell.reg. If you then make a mess of the registry edit, or you want to restore the registry back to its previous state, all you need to do is double click the Shell.reg file and the computer will restore it back to its proper place in the registry automatically. A very clever part of Windows. This is a safety precaution you should adopt every time you edit the registry. As long as you do this, you are safeguarded.
Now you can proceed to edit the registry as follows.
Expand the * folder by clicking on the + sign.
You should then see at least one sub-folder named Shellex. Ignore it. If that is the only sub-folder, then create a new sub-folder by Right clicking the * folder. Select New/Key. Name it Shell. If there is already a Shell folder, omit this step. ( A "Key" shows up as a folder in Regedit).
Right click the new Shell folder which you have just created (or the existing one if there was one already there) and again select New/Key. Name it Notepad. Right click the Notepad folder, again select New/Key and name it Command.
Now you should see a chain of folders from * to Shell to Notepad to Command.
Now double click the Command folder. This will display a name/data value box on the right-hand pane. Right click on the "ab" icon in that pane and select "modify".
In the "Value Data" box, carefully copy the pathname, followed by one space then "%1" in quotes. eg notepad.exe "%1". Click OK and you should now see the pathname in the right-hand pane. Close or minimise Regedit.
Now return to your computer and you should see Notepad whenever you right click any file. Try it on a .txt file. If it won't open the file, remove the quotes around %1 and try it again. Some programs seem to need these quote marks, others do not.
Windows may possibly ask for path first time you use this, in which case select browse and navigate to Notepad .exe file. Thereafter it should remember.
Repeat the same procedure for any other entries you want in the right menu (you won't need to create the Shell folder again, just proceed from "Right click Shell folder".) "Shell" is actually your right click menu, although that menu does contain other entries that you can't so easily tamper with.
If it all works OK, you can now delete the exported Shell.reg file.
Finally, export your new Shell folder from Regedit to a floppy. Then you will be able to restore it if you ever need to replace your registry or reinstall Windows.
Copyright Don Penlington