McCain's campaign runs Windows:

widget:~ jim$ telnet <http://www.johnmccain.com>www.johnmccain.com 80
Trying 64.203.107.147...
Connected to <http://www.johnmccain.com>www.johnmccain.com.
Escape character is '^]'.
HEAD /index.html HTTP/1.0

HTTP/1.1 404 Not Found
Content-Length: 1635
Content-Type: text/html
Server: Microsoft-IIS/6.0
X-Powered-By: <http://ASP.NET>ASP.NET
Date: Tue, 03 Jun 2008 22:58:07 GMT
Connection: close

Connection closed by foreign host.