> about IIS tuning other than the "install apache2" kind of fix

That's good one!

Or on a more serious note: http://blogs.zdnet.com/threatchaos/?p=311&tag=nl.e550 (the article is about security, but the two graphs are of interest)

Also beware of the new kid in town http://moodle.org/mod/forum/discuss.php?d=83722#p371729

Finally have a look at http://docs.moodle.org/en/Performance#Operating_System and http://moodle.org/mod/forum/discuss.php?d=54123#p246809