What program to open the jj os 1 file to copy it to my mpc?

I just bought a mpc1000 and it has the password already for the jjos 1 4.99 but the dude I got it from put it back to the original Akai os. I went to the jjos website to download it. My computer says it can't open this file. I have Vista. Someone mentioned using Notebook to open it and I did. It opened but now I have this wierd encrypted file that I can't drag and drop. HOW do I get that to my mpc? Thanks!

Maybe a more simple straight forward question is: WHAT PROGRAM SHOULD I OPEN THE JJ OS1 FILE W/?

You don't open the OS file. Just copy it to your Compact Flash card (you do have one, don't you?) and follow the instructions here:
http://www7a.biglobe.ne.jp/~mpc1000/os1_inst.htm

...just to be sure, download the OS file again to start with.