BizTalk SQL Server Consumes more memory

Hi,

The SQL Server which is hosting the BizTalk 2004 Server always consumes
more 
memory (Around 2GB out of 3.5 of available physical memory). The SQL
Server 
occupies the same memory even if the BizTalk processes are not running. If
i 
restart the SQL Server service or the Box itself, then the memory usage
comes 
down to 100MB!!!

I'm quite surprised to see the difference between the memory usage (Before

and after Reboot). What could be the reason for BizTalk SQL Server to hold

large amount of memory even if the processes are not running? Could there
be 
some problem with the BizTalk processes? How to identify and contain this
SQL 
Server behavior

Thanks in advance for sharing your views.