[JAMF]

7z is the compression used by the open source packer/unpacker programme 7zip. You can get it here:
http://www.7-zip.org/download.html


(Open Source is better than nag-ware )

There's a dozen files listed. which one do I need?

1/2 = Windows XP 32Bit / Vista or Windows7 32Bit
3 = Windows XP64Bit / Vista or Windows7 64Bit
Forget 4 and beyond.