I am running Toad for Oracle version 9.7.2.5.
I am running it through Parallels on a Macbook Pro (OS X).
I have installed the Oracle Instant Client 11.1 and 10g.
I have not made any registry settings but have put the folder with the client in the PATH environment variable and set up TNS_ADMIN to point to the file with the tnsnames.ora file.
When I open the Oracle Home Editor, I see 'home is not valid'
Support for Toad on Parallels Desktop and connection to Oracle only tested with a full 10g client.
WORKAROUND:
Install Oracle 10g full client
STATUS:
Enhancement request ST58136 has been submitted to Development for consideration in a future release of Toad for Oracle.