Post Source – vgeek.
Resetting firstname.lastname@example.org is fair easy process, I forgot my password and stopped on this Vmware KB. Putty to vCenter appliance (I am using 5.5) run below tool.
Type 3 to reset and type the distinguished name of Administrator account, In your case it will be cn=Administrator,cn=users,dc=vSphere,dc=local once you press enter key, voila! It generates a new password and shows you on the screen.
Select Users and Groups, right click Administrator or there is an edit user button on the top and change the password which you can remember easily.
Now log off from vmware web client and try with new password.