How to verify if your exchange 2007 is running on SP1

You can check the Version of the server. If the version is 8.1 (Build 240.6) then it has Service Pack 1 Installed, If it is 8.0 (Build 685.24) it is RTM

You can check the version from the conosle -> Exchange Management Console -> Server Configuration. All the Exchange Server with Roles and versions will be listed in the Middle Pane on the right side.

You can also check the version using power shell commandlet
Get-ExchangeServer -Identity YourExchangeServerName