installing Visio 2007 with startup script

For the past week or so I've been working on a deployment process for
Visio 2007. I am in a very small environment with about 50-60
computers, so I decided a computer startup script would be best. Good
news is that I have been able to get Visio 2007 to install via several
different methods (using the config.xml file, using the .msp file,
etc.) without any problems, but the bad news is that I have not been
able to successfully get it to uninstall Visio 2000. If I launch the
install locally using the setup.exe and .msp file it uninstalls 2000
without any problems. It's only during the computer startup script
that it doesn't uninstall. Has anyone had any success with getting
the previous version to uninstall correctly using the startup
scripts? I've even tried copying the installation files to the MSO
folder using the config.xml file, and then using another script to
launch setup but that still doesn't uninstall 2000. Any insight would
be much appreciated. Thank you!