The settings of a "Temp" folder available in the control menu are for the server part of the application only. Presumably, the pathname to “Temp” folders for workstations remains the same as default, to provide more compatibility in a heterogeneous network. However, you can change it manually!
C:\ProgramData\Novosoft\
(Here the [username] is a name of a user who own the instance of Handy Backup.)
C:\TMP\
See also: FAQ | Network Server Backup:
⇒ The Standard edition is a client for the Network edition, isn′t it?
⇒ Can I back up workstations if my server is not in the same domain?
⇒ The list of workstations is empty or lacks some of the networked computers. Why?