IIS worker process isolation mode
I found my IIS server crashing more often than usual, and although a net stop w3svc / net start w3svc was bringing it up to speed again. I couldn’t rely on this to keep the server going on a long-term basis
I looked in the Event log, and found a recurring error which read "It is not possible to run two different versions of ASP.NET in the same IIS process. Please use the IIS Administration Tool to reconfigure your server to run the application in a separate process.". As readers of this blog will know I have .NET 2.0 beta 2 installed on my server, along with .NET 1.1. So I read up on the Microsoft Technet site about IIS worker processes, and it seemed to recommend this course of action
* Create a new Application Pool specifically for .NET 2.0 apps.
* Right click on a .NET 2.0 website (in my case www.downloadsoft-ware.co.uk) click on Home directory. Then under the drop down box for application pools, select the .NET 2.0 app-pool.
And it hasn’t crashed since. But I’ll leave it for 24 hours.
Network Programming in .NET 