I completely understand your frustration, really I do as malware and all that crap is the worst we have on the web these days.
But I hope you understand me, I am protecting my hard work and I can assure you (although like anything there is never 100%) I am 99,9999999999% sure we do not host malware and where we do see something we always
add an installation note and/or warning where we inform the user we saw some behaviour and installation is always upon your own risk.
But, onto your issue, let me quote this:
with z opener
Did you install that program? If so, by the name of it I can guarantee you that is the issue.
download from here: http://www.7-zip.org/
Any other site and or program you use (winrar is also safe) might result in you getting stuff you do not want.