I hit a problem where I needed to enable network access to SQL Server 2008 Express R2 which was on a Win7 64bit OS. the solution was previously posted at: http://www.sevenforums.com/system-security/58817-remote-access-sql-server-express-2008-windows-7-a.html
Here are some step by step details for getting this to work:
1) Enable remote connections to Sql Server. (SSMS, connect to DB, right-click and select properties and then Connections…make sure remote conenctions chkBox is ticked).
2) Set up Inbound and Outbound rules for TCP port 1433
3) Set up Inbound and Outbound rules for UDP port 1434
4) Set up inbound and outbound exceptions for sqlservr.exe. I am running a 64 bit machine so this file was located here: C:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\Binn\sqlservr.exe
5) Set up inbound and outbound exceptions for sqlbrowser.exe. Again, I am running a 64 bit machine so the file was located here: C:\Program Files (x86)\Microsoft SQL Server\90\Shared\sqlbrowser.exe
And thats it.