I have Microsoft Windows 2003 Server Enterprise Edition, and Exchange Server 2003 (SP2) installed on it, I am suffering from failure on logon to my exchange as the RPC service always halt. I troubleshoot the problem, but I see nothing in the even viewer about it. I have 200 mailboxes, and I think that it may be because of the growth on the mailboxes, I think Microsoft has a patch to increase the mailbox database to 17GB instead of the regular 8GB I appreciate your help

Halting services would typically result in an event viewer entry in the System log. I don't think the size of your mailbox database would be the most likely issue here. In Exchange Server 2003, Standard Edition your Mailbox Store usage may grow to 16GB (not 8GB). A little change in the registry allows you to stretch this limit to 17GB temporarily. (to solve problems) With Exchange Server 2003 SP2, Standard Edition you can stretch the limit of Mailbox Store usage up to 75GB. This is also done in registry.