Mike Lagase wrote a great blog post on his blog talking about two issues (we have fixes for both) that can cause excessive paging on your Exchange 2007 servers.
Those fixes are described in two KB articles:
FIX: You may notice that the memory load is very high when you run an application that is built on the .NET Framework 2.0
A Windows Server 2003-based computer becomes unresponsive because of a memory manager trimming operation that is caused by an indeterminate module that requests lots of memory
I would definitely suggest that you go over to Mike's blog and learn more about it, as he explains how to narrow those problems down and see if they are causing performance issues on your server!
- Nino Bilic