wont install please help   

I have zoo tycoon 2 zoo keeper collection and I tried installing the marine 
expansion pack and it went really slow my friend recommended that I 
uninstall and then reinstall it but when ever I try to install the the zoo 
keeper collection and I then click on install it always says uninstalling 
and wont let me reinstall please can some one help.
thank you

date: Wed, 12 Mar 2008 20:19:30 -0000   author:   madadam