sis is: Nokia Mobile Phone File Format. It can be opened with Symbian operating system.
Sis is a old version game format for Nokia mobile phones. With correct emulator these kind of games can be opened on computers.
In the new versions of this game formats, instead of .sis file extension .sisx extension is being used. If your mobile phone is not compatible, you are not able to do direct conversion between .sis and .sisx. You should find different version of the game.
Sis File format viewers or openers
Symbian operating system, Convenient Nokia mobile phone
Sis File related links.