do something like this:
code:

read registry for both mcafee versions
if error reading registry
   check probable install dir for the old exe
   if exe doesn't exist
       install new mcafee
       force reboot
       else
       net send for MIS support for hands-on 
compare it the the current version
if installed is less than current version
    read registry for uninstall string
    uninstall old mcafee
    force reboot
<addl code to update dat files>
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