How can I install SQL Server client tools in unattended mode?

A. The Microsoft provided setup.inf file with 6.5 and below doesn't allow for this (haven't checked out 7.0 yet), so your choices are :-

1. Amend the setup.inf to provide this support, or write a new one.

2. Do a script to copy the relevant files across and update any registry parameters needed. You could use something like sysdiff to do this.