The error is displayed if you do not have admin rights.
To solve this issue, login as a user with admin rights and repeat the installation (selecting install for everyone option).
Alternatively whilst still logged in as user without admin right, run the following from command line:
Code:Runas /user:<UsernameWithAdminRights> 'C:\Downloads\IntelliSMSOutlookAddin.exe'
Replace:<UsernameWithAdminRights> with a username that has access rights, e.g. Administrator
'C:\Downloads\' with the location of the downloaded IntelliSMSOutlookAddin.exe file
Technical Notes:
When install runs it attempts to replace C:\Windows\UnInst.exe with the latest version. If it is unable to replace this file, it wrongly assumes that unInstallShield is running. It provides a misleading message to the user. Even if this InstallShield problem was not present it still would not be possible to install the Outlook Addin as Admin right are required to register the COM component (i.e. even regsrv32 will fail).
