Download problem with Quick time

I'm a very new mac user and some things are hard for this old head to get around so these forums are great so thanks in advance

Problem Opened mininava clicked on Mac OS X Leopard for Dummies zip in the download this torrent

Have a choice of open with?

or save to disk

Opened with save to disk ok

then OPEN

then message application was downloaded from inter-net and will be opened with Quick Time are you sure you want to open

Hit open

THEN😡 get this

This movie could not be opened 🙁

how do I get around this issue

LOZ