Recently I've seen people having trouble with .zix extension files. The PSP ISO they obtained contains a .zix file, and they were encouraged by the readme to download and install a "free" compression program called Winzix. Please DO NOT install winzix. It contains numerous spyware/trojan not easily removed, even after uninstalling the program. And If you come across a .zix file, just delete it. DO NOT install winzix for your own sake! If you happened to install winzix, there is a way to extensively remove all malware from it. For more info, please refer to here.