Thanks all for your help.
I will check Bert's question on memory but I think it is very likely that there are memory resources that are being used by SQL and not released.
I have ordered more memory. Upgrading to the AC latest version does not help. I have trend for SMB with latest version.
Server 2003 seems more or less stable, expensive and I eventually figured out I would have to administer it myself as the local folks were expensive and not more tech savy than me. Rebooting is not quick with exchange and all the other services needed.
