Improving Site Speed and Cache for Authenticated Users
I created a presentation that covers some of the basics of of performance https://docs.google.com/presentation/d/1AgnurTWsWdMAFjfFmSU7mk2zfJu8jG_KmVdZ7-o6Pok/edit#slide=id. In your case I would make sure poormans cron in core is disabled, use an IP for your database connection (very important on IIS), make sure you have some sort of op code caching enabled, and follow this guide (linked in the presentation under Basic database tuning) to fix database issues at the drupal level, and be sure to adjust some MySQL defaults as well.