I'm trying to make a jar file but it never seems to work.

I have three class files, one with the main method, in the folder "hexMaze." In command prompt, I go to this directory, then type in "jar cvf HexMaze.jar *":
C:\Documents and Settings\Aaron MacDonald\Desktop\hexMaze>jar cvf HexMaze.jar *
added manifest
adding: HexArray.class(in = 3460) (out= 2057)(deflated 40%)
adding: HexCell.class(in = 2780) (out= 1390)(deflated 50%)
adding: HexDisplay.class(in = 1538) (out= 940)(deflated 38%)

C:\Documents and Settings\Aaron MacDonald\Desktop\hexMaze>
This makes the file HexMaze appear in my hexMaze folder. However, when I double-click it I get this error message:
Failed to load Main-Class manifest attribute from C:\Documents and Settings\Aaron MacDonald\Desktop\hexMaze\HexMaze.jar
I also get this error message when I try to make my jar inside Eclipse. Can anyone tell me what's going on?

If it helps, I'm using jdk 1.5.03 on Windows XP. I believe my PATH variable is right, since I'm able to compile through the command promt (though when I try to run a file in the promt I get a bunch of NoClassDefFoundErrors...).