Q. I have an Exchange Server 2003 server that runs on Windows Server 2003 and has more than 1GB of memory. What settings should I add to the boot.ini file to optimize virtual-memory usage?

Please reading the following update , very important.

http://bink.nu/Article4438.bink

/3GB
Increases the size of the user process address space from 2 GB to 3 GB (and therefore reduces the size of system space from 2 GB to 1 GB). Giving virtual-memory- intensive applications such as database servers a larger address space can improve their performance. For an application to take advantage of this feature, however, two additional conditions must be met: the system must be running Windows XP, Windows Server 2003, Windows NT 4 Enterprise Edition, Windows 2000 Advanced Server or Datacenter Server and the application .exe must be flagged as a 3-GB-aware application. Applies to 32-bit systems only

PAE is a physical extension and has nothing to do with virtual memory. To address issues with VM fragmentation if you are running Win2k advanced or datacenter you can use /3GB switch, if you are running standard your best bet is reducing the RAM to around 1 GB and implementing tewaks per follwing KBs. 325044 How to troubleshoot virtual memory fragmentation in Exchange Server 2003
http://support.microsoft.com/?id=325044
317411 How to gather data to troubleshoot Exchange virtual memory issues
http://support.microsoft.com/?id=317411
317411 How to gather data to troubleshoot Exchange virtual memory issues
http://support.microsoft.com/?id=317411
315407 XADM: The "HeapDecommitFreeBlockThreshold" Registry Key
http://support.microsoft.com/?id=315407

Exchange and PAE is not a good idea. Exchange is not built to understand anything over 4GB. The /PAE (Physical Addressing Extensions) switch is a parameter that is set in Boot.ini. The /PAE switch enables a computer to access more than 4 GB of physical memory (RAM). Exchange Server cannot use more than 4 GB of physical memory, and there is no benefit to installing more than 4 GB of RAM on a computer that is dedicated to running Exchange Server. This switch may have been incorrectly set an OEM Setup program.
If the server is running another memory-intensive application (such as SQL Server 2000), this switch may have been intentionally set by an administrator to use more than 4 GB of RAM. If you are running multiple applications that require the additional memory, you can run a Windows hotfix that will help prevent Exchange store failures that might occur when there is more than 4 GB of RAM available. Note that the recommended best practice is to dedicate a computer to run Exchange Server only. For more information about the hotfix, see Microsoft Knowledge Base article 834628, "Data is corrupted when PAE is enabled on a Windows Server 2003-based computer" ().If the computer where this warning was generated is a dedicated Exchange Server computer, remove this switch from the Boot.ini file.

Can I use this settings on Windows 2000 Server with Exchange 2000 Server ?
Because, I have some problem with Virtual Memory Fragmentation.