ok i have two things to ask here. for 1 what i a DAt file and what program do i use to open them?

and for 2 what to do when i download? everytime i go to download a file/program it ask do i wish to save to disk or open. i have always picked open and it does the job most of the time but some times if i dont save it to disk it will not work.

how do i know when to save to disk or just to open it? thanks for all your help.

p.s. i can't beleave i am sitting here playing madonna. shoot me