Multiple DB instances on one workstation

I have two DB’s on my Thinkpad.
One SQL6.1 DB for application A, one SQL7 DB for application B.
I have configured PC to need to reboot to correctly process SQL.INI and SQL.CON file in order to get the ODBC driver to recognize each database app and database as separate programs.
This is time consuming, as when I go from application A to B, I need to reboot.
Any better ideas?