If you right click on the START button but do not see a context menu. This is due to a corrupted or missing folder:

c:\User\<user>\AppData\Local\Microsoft\Windows\WinX

The solution is just to copy this folder (and its three subfolders) from a working machine or working user account on the same machine.

c:\User\<user>\AppData\Local\Microsoft\Windows\WinX\Group1
c:\User\<user>\AppData\Local\Microsoft\Windows\WinX\Group2
c:\User\<user>\AppData\Local\Microsoft\Windows\WinX\Group3