VERIFIED SOLUTION i
When installing Mail360 v2.1 Server on Windows Server Enterprise 2008 x86 (service pack 2), the installer starts installing and then throws an error 'the system cannot open the device or file specified'.
This could be caused if installer is not launched using elevated privileges.
ResolutionUPDATED: September 26, 2017
Use elevated privileges (i.e using "Run as Administrator") option to launch the installer.