cannot open client

I have been playing off of a .jar file for the past couple of days but i restarted my computer a little while ago and for some reason it would not upload the client anymore. I deleted the old file and redownloaded the file and now that it is in another file i can not find where the client is loacated at. It was in a jar file that i could not open, then it became a zipped file then i unzipped it so i could accesss it and now i have no clue where it is at prety much. Help would be greatly apreciated!