When you install Exchange 2007 Service pack 2 or 3 on a server running Forefront for Exchange, you will encounter the below error:

Error: Setup has detected that Forefront Security For exchange server is running on the server and has to be disabled before Exchange Server 2007 is upgraded.

Before you can apply a service pack for exchange 2007, you need to carry out the below tasks:

1) Stop the services listed below
FSCController
Microsoft Exchange Transport
Microsoft Exchange Information Store

2) Next, open a command prompt. If running Windows 2008 server, right click command and run as administrator.

3) In the command prompt, change the current directory to C:\Program Files (x86)\Microsoft Forefront Security\Exchange Server

 4) Type fscutility /disable   
The command above will start to remove dependencies and the final result should be Status: Microsoft Forefront Server Security NOT integrated

5)  Now, install your Exchange service pack

6) When the installation is complete, you must reenable Forefront Security for exchange. To do this, stop the below services.
Microsoft Exchange Transport
Microsoft Exchange Information Store

7) Open a command prompt as you did in step 2 above..

8.) Change the current directory as you did in step 3 above

9) Type fscutility /enable

10) Start the below services
FSCController
Microsoft Exchange Transport
Microsoft Exchange Information Store