Exchange 2013 will not install on Domain after failed install

I have had an install of Exchange 2013 on Windows 2012R2 fail.

I then proceeded to uninstall Exchange which appeared to go through fine.

Even after reinstalling the whole of Windows on the server, there appears to be something left on the domain that is stopping the install.  

The install fails when trying to install the mailbox role, it fails with the following message:

The following error was generated when "$error.Clear(); 
          if ($RoleIsDatacenter -ne $true)
          {
            if (test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
            {
              # upgrade the discovery mailboxes to R5 version, this will fix the RecipientDisplayType property of the discovery mailbox which was wrong in R4.
              get-mailbox -RecipientTypeDetails DiscoveryMailbox -DomainController $RoleDomainController | where {$_.IsValid -eq $false} | set-mailbox -DomainController $RoleDomainController
              $name = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxUniqueName;
              $dispname = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxDisplayName;
              $mbxs = @( get-mailbox -Filter {name -eq $name} -IgnoreDefaultScope -resultSize 1 );
              if ( $mbxs.length -eq 0) 
              {
                $dbs = @(get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
                if($dbs.Length -ne 0) 
                {
                  $mbxUser = @(get-user -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
                  if ($mbxUser.Length -ne 0) 
                  {
                    enable-mailbox -Discovery -identity $mbxUser[0] -DisplayName $dispname -database $dbs[0].Identity;
                  }
                }
              }
            }
            else
            {
              write-exchangesetuplog -info "Skipping creating Discovery Search Mailbox because of insufficient permission."
            }  
          }
        " was run: "Database is mandatory on UserMailbox.".

Error:
The following error was generated when "$error.Clear(); 
          if ($RoleIsDatacenter -ne $true)
          {
            if (test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
            {
              # upgrade the discovery mailboxes to R5 version, this will fix the RecipientDisplayType property of the discovery mailbox which was wrong in R4.
              get-mailbox -RecipientTypeDetails DiscoveryMailbox -DomainController $RoleDomainController | where {$_.IsValid -eq $false} | set-mailbox -DomainController $RoleDomainController
              $name = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxUniqueName;
              $dispname = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxDisplayName;
              $mbxs = @( get-mailbox -Filter {name -eq $name} -IgnoreDefaultScope -resultSize 1 );
              if ( $mbxs.length -eq 0) 
              {
                $dbs = @(get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
                if($dbs.Length -ne 0) 
                {
                  $mbxUser = @(get-user -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
                  if ($mbxUser.Length -ne 0) 
                  {
                    enable-mailbox -Discovery -identity $mbxUser[0] -DisplayName $dispname -database $dbs[0].Identity;
                  }
                }
              }
            }
            else
            {
              write-exchangesetuplog -info "Skipping creating Discovery Search Mailbox because of insufficient permission."
            }  
          }
        " was run: "Database is mandatory on UserMailbox. Property Name: Database".

Any ideas?