is a program that unzips files a necessity for zplug instalation?
isnt a unzip software a necesarity in general?
brian20, I also had no unzip program at the beginning. 
An unzip program isnt very expensive though and its always good to have one but for now you can download a trial version of an unzip program and download all the Zbrush plugins that you want and unzip them then.
Hasn’t Windows Explorer been able to open zip files natively since XP. Macs are able to do so as well.
Richard
@ Richard: Good question Im a PC user (windows vista) and I just realized that I didnt install my unzip program after my computer crashed so it must be possible without.
Windows has a generic one that can open .zip files which actually started with windows xp i believe --maybe millenium :-(. However, depending on the compression, some .zip files are unrecognized the same way .rar files are within the generic program. I would suggest using winrar (its free to try–and then it seems the trial never runs out) or winzip which is ancient but still kicking. The biggest thing to take note of is to make sure when extracting to keep the file integrity. Otherwise, your plugins may not work. Dragging it from within the compressed file to your desktop or wherever the desired location may be doesnt always keep the integrity so be careful.