Plus, if I look at the 'appended' data manually in regedit, all I see is the new value and not the old value so I'm not sure what 'append' means in this case.

So what happens in the next update? How do I have this registry value not right over any previous value? Currently the value is a REG_SZ but if I append/prepend it changes to a REG_MULTI_SZ and all of a sudden my program's code does not recognize it. Previous customers will get the named value in the update and that will get a special value. To enable Windows Installer logging yourself, open the registry by using Regedit.exe, and then create the following subkey and keys: Path: HKEYLOCALMACHINESoftwarePoliciesMicrosoftWindowsInstaller Type: RegSZ Value: Logging Data: voicewarmupx The letters in the value field can be in any order. So new customers will have this named value and it will be filled with a real value when they register. So previous registered customers do not have this registry key named value so I put it in the updater and that only gives me the choices of Prepend, Append, or Replace any existing values. This value gets set in the program when the user finally registers the program during the trial period. In the most recent version of the installer I have it set to create a registry key with a named value of RegDte ie registration date.

Advanced installer registry