Location of the tnsnames.ora file in 10.2.0.1 instant client

I am trying to use Oracle Instant Client to connect to a 10g database from SQL Server and I am getting "ORA-12154 TNS:could not resolve the connect identifier specified". I have a tnsnames.ora file located in the ..client_1\network\admin directory with the correct database alias in it.

My questions:

1. How can I determine whether my problem is because the client is not finding the tnsnames.ora file or if it id because the entry for the database in incorrectly specified?
2. If the client is not finding the file, what registry key and name do we have to set to force it to look in the correct directory?

Thanks,
Peter Schauss

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