Minimum files required to access Oracle data

Background:

I have a 64 bit VM Win 2008R2 server that's running a Lotus Domino server.

I need to install files on this server that allow it to communicate with Oracle.

On an older 32 bit server, we installed a full Oracle client and that worked fine.

My intention is to try and not do a full up client install but to put only those files necessary to allow communications to work.

I need to know the files that are necessary, where they go, and any configuration/path values that are mandatory.

If the setup differs based on version of Oracle, then let's look at 10.2.0.2 and 11.2.0.2.0.