The installation program (or most installation programs) detect if the
program is already installed. If it is, it shows options to remove it.
I would either try following through (remove the application, then install
it again),
and if that doesn't work, I would try a Windows Install Cleanup. To do
that, download and install this program from Microsoft:
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http://download.microsoft.com/download/e/9/d/e9d80355-7ab4-45b8-80e8-983a48d5e1bd/msicuu2.exe
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Run that program, find the Zoo Tycoon Expansion program listed, highlight it
and choose remove.
NOTE: TRY TO UNINSTALL USING THE NORMAL WAY FIRST, WITH THE INSTALLATION
PROGRAM THAT PROMPTS YOU TO UN-INSTALL. BECAUSE --> this Uninstall Cleanup
Utlity does NOT uninstall programs, it just removes the record that they were
ever installed in the first place, allowing you to reinstall it normally.
DO NOT USE THIS UNINSTALL CLEANUP UTILITY TO UNINSTALL NORMAL APPLICAIONS.
ALWAYS TRY TO USE THE CONTROL PANEL'S ADD/REMOVE PROGRAMS APPLET.
(I don't normally scream (use all caps) but this is really important, that
uninstall utility can do damage if you use it for programs that are working
okay).
- skeene