After switching IIS to 32-bit on our 64-bit server in order to run the

IIS appears to be returning "Service Unavailable" when it is unable to load the appropriate ASP ISAPI DLL to process requests for ASP pages, though static HTML pages are usually also affected by this problem.

A1. The first step in attempting to resolve this issue is to reset the ASP.NET component in IIS. To do this, open the command line and navigate to the following directory:

%SYSTEMROOT%\Microsoft.NET\Framework\v2.0.50727\aspnet_regiis.exe -I

A2. Then make sure that the status of ASP.NET 2.0.50727 is set to Allowed in the Web service extension list in Internet Information Services Manager.

A3. Restart IIS by right-clicking the computername in IIS, selecting "All Tasks -> Restart IIS".

If you are still receiving the "Service Unvailable error", then try the following:

B1. In IIS, right-click "Web Sites" and click the "ISAPI Filters" tab. Make sure that ASP.NET_2.0.50727.0 is listed with a green arrow.

B2. If it is not listed, click the "Add" button and manually specify the path to the Executable as %SYSTEMROOT%\Microsoft.NET\Framework\v2.0.50727\aspnet_filter.dll and specify any descriptive name under "Filter Name", e.g. "ASP.NET 32-Bit"

B3. Navigate to "Web Service Extensions" and make sure that ASP.NET v2.0.50727 is listed as Allowed.

B4. If it is not listed, right-click in the white area and select "Add a new web service extension". Specify a descriptive extension name (e.g. ASP.NET 32-Bit), check the "Set extension status to allowed" check box and add the file %SYSTEMROOT%\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll to the list.

B5. Repeat steps A1 and A3 and try to access the ASP pages again, you should now have access.

Please see the KB article below for more information on this 64bit issue.