Hello,
The error looks to be related to your environment settings, not the permissions granted to the Adaxes service account. Most probably, it is about UAC. As an option, you can try running the installation as administrator. To do so, start command prompt as administrator and use the below command. In the command, <path_to_package> is the path to the Adaxes installation package.
msiexec /i "<path_to_package>\adaxes.msi"