- Are they on the same network (not separated by router)?
- Is there no firewall rule blocking the connection?
- Do you have a dedicated machine that can run the sql server all the time it could be needed?
- Let's suppose "connect all" means connect from all clients to the same sql server.
- Let's suppose you are using Microsoft SQL Server 2005 or above (the links below assume 2008)
If these requirements are satisfied:
1) After server and database installation enable remote connection: http://blogs.msdn.com/b/walzenbach/archive/2010/04/14/how-to-enable-remote-connections-in-sql-server-2008.aspx
2) Set proper connection strings on client side: http://www.connectionstrings.com/sql-server-2008
3) You might need to set up logins on the server and database users, depending on what your authentication scenario is.