The information was in the SP1 Readme
"Event 9665: Update to recommended memory settings for running Exchange Server 2003 SP1 on Windows Server 2003.
When you are running Exchange 2003 SP1 on Windows Server 2003 with more than 1 GB of RAM, it is recommended that you set the SystemPages registry key to zero. This recommendation contrasts with the recommendation for Windows 2000 Server, which is to set SystemPages to a value between 24000 and 31000.
The recommended memory settings for Exchange 2003 SP1 on Windows Server 2003 with more than 1 GB of RAM are as follows:
If you host mailboxes or public folders on a server with more than 1 GB of RAM, make sure that the boot.ini file contains the /3GB switch.
When you use the /3GB switch, add the /userva switch to the boot.ini file and set the switch to a value between 2970 and 3030.
When you use the /3GB switch, set the hexadecimal value of the following registry key to 0x00040000:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\HeapDeCommitFreeBlockThreshold
Set the decimal value of the following registry key to zero:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\SystemPages
If you set SystemPages to the Windows 2000 Server recommended value of between 24000 and 31000, an Event 9665 will appear in the event log.
See url below for full text
http://www.microsoft.com/technet/prodtechnol/exchange/2003/library/default.mspx 
