Trying to re-install Exchange even after following all MS best practice guidelines fails with the error:

To install the first Exchange server in a domain, or to run setup in “/ForestPrep” mode, you must be an Exchange Full Administrator at the organization level. You must use an account that has been granted the Full Exchange Administrator role on the Exchange organization using the Exchange Administrative Delegation Wizard. — ID:64283.

Start ADSI Edit.
If it is required, click Default (Domain or Server that you logged in to) in the Computer area to connect to the domain controller, and then click OK.
In the navigation pane, expand the following items:

CN=Configuration
DC=Domain_Name
DC=com
CN=Services
CN=Microsoft Exchange
Right-click the CN=Organization_Name object, and then click Delete.
Click Yes in every adsiedit dialog box that prompts you to confirm the deletion.
Right-click CN=Microsoft Exchange, and then click Properties.
On the Attributes tab, under Select which properties to view, click Both.
From the Select what property to view menu, select Heuristics.
To reset the Heuristics property, click Clear, and then click Apply. The Value(s) field will have a value of not set.
Exit ADSI Edit.