nginx , lighttpd or iis for file hosting?

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http://serverfault.com – i have a vps 4gb ram , 500gb ssd hard disck. i want use this vps for movie download site 700 or 1gb files direct link. whats Your best solution for this work ? linux and nginx/lighttpd or windows and IIS? if you recommend IIS , Which one windows version better fo my vps 4gb ram ? 2003 , 2008 or 2012 ? (HowTos)