I believe that you need to restart the instance before the max memory takes effect. It certainly does work (and needs to be set) on 64 bit.
100 MB's a little low for SQL Server. How much memory do you have on that server?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability