I'm using Vista 3508, with IE7, and when I go to my personnal internal
web site (running, hum, on my linux computer), which is https with a
self-signed certificate, IE7 goes red, and I can't find how to save the
certificate to the certs directory.

I have read an article on the Microsoft site that Microsoft Update in
Windows Vista will allow updates to be downloaded from one computer and
distribute them to other computers across the network to save redundant
update downloads.