It is normal for the STORE.EXE process to consume lots of memory. The Exchange Information Store has an internal feature that enables Exchange to safely monopolize available memory resources. This feature, the Dynamic Buffer Allocation algorithm, is responsible for returning memory to the operating system if other programs require it. If other programs don't need any memory, Exchange uses it all. This is a good thing because, after all, that is why the memory is there. That said, there are good reasons why you may need to tune Exchange 2003. Have a look at http://support.microsoft.com/default.aspx?scid=kb;en-us;815372 for details on how to optimize memory for Exchange 2003.
This was first published in March 2004