Me too, I can't do anything with that.
A 7z extension is basically a zip file, if u have winzip or winrar, you should be able to unpack it, playstation emulator games are packed using this alot, in fact heres a link to the unpacker i use for my psx 7z roms, dont worry its free http://www.7-zip.org/ once you download it, you canm unpack or look in the 7z file just like a zip file. theres also a thing called 'unecm' u can get, where you just drag n drop the file over the app in the folder the app is in, and it automatically unpacks it...but icant remember if it does 7z files, worth checking just in case. hope this helps as not alot of people know what a 7z is.