If you choose to Install portable version., you'll be prompted for a location to install MailStore Home, MailStore Homewill store it's program files and data directory together.
If you choose to Install on this computer, MailStore Home will be automatically installed on to your local computer under the local Program Files directory and your data will be stored under your local Documents directory. MailStore Home can be installed in a few easy steps The only decision you need to make before starting the installation is whether to install on your computer, or to install a portable version of MailStore Home.