**Topic Moved to the Correct section(From V6 Suggestions Moved to Question and answer Forum)**
Jar file is an installation file for a phone that support with java application
eg : Nokia S40 devices
Sis file is an installation file for a symbian phone.
Eg : Nokia S60 devices,Nokia S60 3rd devices,Nokia S60 5th devices ,symbian belle device etc.
You cant open a jar file from a sis file, you just can open a jar file in a phone which support with jar file
btw,may i know what kind of error message you got?