This is the script I used. Stock standard.
"c:\CiscoSoftPhones\CiscoClick2Call8_1_2674\Media\vcredist_x86.exe" /q
msiexec /i "c:\CiscoSoftPhones\CiscoClick2Call8_1_2674\Media\ClickToCallK9.msi" /qn /norestart
MS .NET Framework 3.5 SP1 was already part of the Windows build so did not have to install it.
All I read I could not find anything to set Registry via the install so the configuration was via GPO.
If the standard Users have local admin type level of permissions you could create a Registry hack and add that to the install script but it work need to be run when the User is logged on as from memory the entries are stored under the USER key in the Registry
