iis 7

I have a d7 site up and running on windows server 2008 r2 with iis 7 and it's running extremely slow. I have been reading about the different caching alternatives and am wondering if anyone here has suggestions about which work best for this configuration. I have both authenticated and anonymous users and the entire site is SSL. I am looking at using authcache (http://drupal.org/project/authcache). I have a couple of questions:
1. Is authcache (with memcache as the handler - http://drupal.org/project/memcache) the best way to go for my set up?

We are currently experimenting with using Drupal 6 (soon Drupal 7) with ASP.Net Forms Authentication and a mildly modified External HTTP Authentication Module. Everything is working great for authenticated users. For anonymous requests everything works well too, with one exception. All PHP Posts by unauthenticated visitors hang until the PHP Timeout and then return a 500.0 Error. This error provides no detail of the actual description of the problem even though verbose logging is on. This is true inside or outside of Drupal.

Hi all!
I got really annoying thing while moving my Drupal site from one Windows server to another and fighting it several days already.
I wanted just to clone the site (Drupal 5.18, MySql 5.1, PHP 5.2.6 all versions remain the same)

Servers config:
OLD: Windows Server 2003, IIS 6 with PHP ISAPI filter, standard auth model
NEW: Windows Server 2008 SP2, IIS 7 with PHP FastCGI module, Classic .NET application pool (operate under Network service), permissions to read on PHP and website folder are gratned for IUSR and NEWSERVER_IUSR.

Both servers are in domain.