Some Web Applications were written specifically for Internet Information Services (IIS) Version 5.0, and need custom configuration changes to function properly with IIS 6.0, which is installed by default with both the Web and Standard Editions of Windows Server 2003. This article will assist in setting IIS 6.0 to run in 5.0 isolation mode.
Open IIS by navigating to Start -> Administrative Tools -> Internet Information Services (IIS) Manager.
Click the plus sign next to the computer name, right-click on the Web Sites folder, and select Properties.
Once the Properties dialog box is open, click the tab which says Services. Inside the Services tab, place a check mark in the field which says, ‘Run WWW service in IIS 5.0 isolation mode’, and click OK.
IIS will prompt you to restart so the changes can take effect. Click Yes.
IIS will restart.
Once IIS is finished restarting, your web sites will now be set to run in IIS 5.0 isolation mode. You will notice the Application Pools folder in IIS has disappeared.
To undo the changes, simply navigate back to the Services tab, and uncheck the box for IIS 5.0 isolation mode.