Failed to create web application: /Root/RequestHandlerExt

If you are on step 3 of the 172 steps required to install OCS 2007 and feel like banging your head against any wall you can find to relieve the pain then it is not unlikely that you are in the position I have been in all day and have been presented with the following error message during the webcomponents.msi installation against (in my case) Windows Server 2008 and IIS 7:

Failed to create web application (-2147024809 /Root/RequestHandlerExt)

The log file, which the OCS installer recommends you look at, contains something like this:

WriteMetabaseChanges: 
Error 0x80070057: failed to create web application: /Root/RequestHandlerExt 
Error 26105 Failed to create web application (-2147024809/Root/RequestHandlerExt) 
MSI (s) (F8!14) [15:33:01:268]: 
Product: Microsoft Office Communications Server 2007 R2, Web Components Server 
Error 26105 Failed to create web application (-2147024809/Root/RequestHandlerExt) 
WriteMetabaseChanges: Error 0x80070057: failed to create ASP App

First check that you have the IIS 6.0 compatibility tools installed (see Lee Desmond’s blog for more info). If you have done this and are still getting this error then several sites mention performing an uninstall of OCS, IIS followed by a re-install as a solution.

In my case this was not really an option as I had several websites running on this computer already. It turns out that this was the issue (unsurprisingly, really) and that the installer is looking for the Default Web Site. I performed the migration of site id 1 to a new site and manually revoked the original configuration of the default web site. The install completed successfully after this. I would say to watch out for the IIS7 mmc snap-in and its massive inability to handle renaming of websites with host headers if you’re attempting this yourself and have sites with host headers, obviously.