Included in one of the recent updates to Exchange Best Practices Analzyer (ExBPA) is a new recommendation for Exchange 2003 servers. There is a Windows 2003 Post SP1 hotfix out for a Terminal Service-Working Set issue. So you may want to just add this to your list when you do your next round of Windows security patching and go ahead and address it.
You will need to contact Microsoft Support to obtain the hotfix as it is not publically available. However, you are not charged for cases where you are receiving a hotfix.