1. Open the Start Menu, then type regedit in the search line and press enter.

2. If prompted by UAC, then click on Yes.

3. In regedit, navigate to the location below. (see screenshot below)

Code:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows

4. To Have Menus Open to the Left

A) In the right pane of Windows, right click on a empty space and click on New and String Value. Type MenuDropAlignment and press enter. (see screenshot below)
NOTE: If you already have MenuDropAlignment, then skip this step and go to step 4Binstead.

B) In the right pane, right click on MenuDropAlignment and click on Modify. (see screenshot above)

C) Type 1 and click on OK. (see screenshot below)

D) Go to step 6.

5. To Have Menus Open to the Right

A) In the right pane of Windows, right click on MenuDropAlignment and click on Deleteand Yes. (see screenshot below step 4B)

OR

B) Repeat all steps in step 4, and type 0 in step 4C instead.

6. Close regedit.

7. Log off and log on, or restart the computer to apply.