7zip is strange. Best compression format I've ever seen. I remember having an image file of Vagrant Story, which was around 700 megs, yet somehow with .7zip, it was compressed down to 90 megs. |: | I digress... Hopefully those maps are fun maps. : )
Vig: a .7z file is a 7zip file. You can get the decompressor here: http://www.7-zip.org/ (sidenote: I have seen 7z compress some HUGE files into tiny ones. Ex: a couple gigs into a couple hundred megs). I didn't have any problem getting it.