I would break out the problem into 2 parts:

- install Firebird engine, if required. (Reminder: you can install 32bit FB engine on 64bit OS) (Reminder 2: if using remote server, you don't need to install FB server)
- make no assumption about the bitness of the client OS for the purposes of your application install (you app is 32bit so you only need to concern yourself with 32bit client)

To install your client I would place the 32bit FBClient.DLL in a Client\ folder under your EXE/install/application folder, and the Firebird MSG file in the install folder. Then have your application explicitly load the fbclient.dll from the application/client folder.

Sean

Good suggestion.

Thanks Sean