You need to use something other than Vista's unzip tool to unpack it. 7-zip is good (handles gzip files, and tar files (from Unix, linux) as well for one thing). See this thread for supporting evidence:
http://www.alice.org/community/showt...ighlight=vista
Also, Vista's unzip tool, at least before I gave up using it, was incredibly slow. I don't recall noticing updates for it.
You can get 7-zip from
http://www.7-zip.org/
As usual, do a bit of research to be sure this is legitimate; you don't know who I am.
Hope this helps.