Could not load all ISAPI filters for site/service. Therefore startup aborted.

You may receive a “Service Unavailable” error when opening CRM in IE. Looking at the eventlog of the CRM server, it seems that Worker Process could not start correctly and show the following entry:

ISAPI Filter ‘C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet_filter.dll’ could not be loaded due to a configuration problem. The current configuration only supports loading images built for a AMD64 processor architecture. The data field contains the error number. To learn more about this issue, including how to troubleshooting this kind of processor architecture mismatch error, see

This occurred on the CRM server for one of our customers after they installed a 32-bit application which also required a website in IIS called SolarWinds-Orion-NPM.
We are not sure if the installer reconfigured the IIS website, or the sysadmin did J

For IIS 6.0, it is not possible to run both 32-bit an 64-bit worker processes.

This is stated here on the MS website:
On 64-bit Windows, the World Wide Web Publishing service does not support running 32-bit and 64-bit worker processes concurrently on the same server.

Anyway, switching the IIS website back to x64 mode solved our problem.

To do this for IIS6.0, run the following script in a Command Prompt:

// this will disable 32-bit mode on IIS
cscript.exe C:\inetpub\adminscripts\adsutil.vbs set W3SVC/AppPools/Enable32BitAppOnWin64 “false”

// this will register the .NET framework assemblies in 64-bit mode for IIS
C:\Windows\Microsoft.NET\Framework64\v2.0.50727> aspnet_regiis.exe –i        

Your CRMAppPool should now start correctly

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Posted in CRM 4
2 comments on “Could not load all ISAPI filters for site/service. Therefore startup aborted.
  1. suresh says:

    please could you tell what should be the solution for same issue in IIS7

  2. Tanus Sacin says:

    Awesome! , I was fighting with this problem for a couple day.. thanks a lot

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