InstallAware

I'm trying to use the SQL Server plug-in in my installer to connect to a SQL Server 2005 database, and have an issue with the following scenario. If I run the installer on Server A (which does not have the SQL 2005 Client tools installed) and it connects to a database on Server B, the script fails. However, if I install the SQL 2005 Client tools on Server A, suddenly the script starts working. I'm assuming I shouldn't need to install those tools on Server A to run the script, so is there some subset of that installation that needs to be on Server A that I'm missing?

I discovered that SQL Server Native Client (included in SQL 2005 Client tools) is what needed to be installed on Server A to get it working. Any ideas why this is the case?