IIS/ASP.Net Configuration
The following changes are recommended in order to optimize the performance when the application is accessed by a large number of users. These changes should be made before installing IRC.
Note: Before making any changes to the configuration files, back up the
machine.config file and aspnet.config file as the changes will affect the
default IIS settings.
After making these changes, restart the application server.
For details refer to the article http://support.microsoft.com/kb/821268 and http://blogs.msdn.com/b/tmarq/archive/2007/07/21/asp-net-thread-usage-on-iis-7-0-and-6-0.aspx