The service can be run as the System Account or as an NT domain account. Ensure that your provide a full path plus extension. This means that the subprocess monitor will attempt to restart the service if it fails. Mask is the Affinity Mask of the subprocess. The mask is merely a bit map of which CPU's you want to run your process on.
Priority is the sub-process priority.
Interact allows the application to interact with the desktop when logged in on the console. FireDaemon makes NO checks as to whether the service it is deleting it actually created. Windows NT 4.0 SP4 or later is required. The -r switch is used in post installation to propogate environment variable changes. Refer to MS Knowledge Base article Q104011.