Exchange 2007 Mailbox Role fails to install on 2008 R2

I run into a situation today:

While installing Exchange 2007 SP1 on a Windows 2008 R2 server, Mailbox role was failing to install with an “Access denied” error.

I tried using the Add-ADPermission command:

Get-Mailbox -RecipientTypeDetails usermailbox | Add-ADPermission -ExtendedRights "send as" -User "domain\domain users"

to give all the mailboxes that are "usermailbox`s" "the send as" ExtendedRights.

But that did not work…

So what was the solution? Heh.. You’ll never guess..

I simply run the Exchange setup.exe in compatibility mode.

Here are the steps:

1. Right–click the setup.exe icon. 

2. Click Properties. 

3. Click Compatibility tab. 

4. Click Run this program in compatibility mode and select “Windows Vista”.

5. Click OK.

And that did the trick!

Note: Don’t bother installing Exchange 2007 SP2 because it is not supported for 2008 R2.