How can we achive the replica of databases for SQL Server? I have been working in VB6 to VB.NET migration project.In VB6 project they have individual databases (access db .mdb) for every user now we made that to centralized database using SQL Server.

In the old application we have a MasterDB.mdb which is in sync with the local.mdb. Some times we need to sync with both the users of local.mdb. After a particular interval of time we need to sync with the MasterDB.mdb.

We need to do this in SQL Server. So, I have a done more analysis related to SQL Server. I read a MSDN forums and many articles related to replication in SQL Server (Related Scenario). I think that merge replication matches to my requirements. 

Can anyone suggest whether I have chosen the correct replication? Do we have any environment changes to set up this replication?
To reinforce what Jon says - a single DB to which all clients connect all the time, with the schema designed accordingly, will be a much better solution.  You only need replication in a few circumstances.  One is if a client machine must be able to work while disconnected.  Another will be if there are huge latency issues between your various sites.  Replication, especially two-way merge replication, can be a huge pain - during upgrades, for example.