Using ArcGIS Server with a 64-bit processor

http://resources.esri.com/help/9.3/ArcGISServer/install_gds/dotnet/Using_ArcGIS_Server_with_a_64-bit_processor.htm

ArcGIS Server 9.2 and higher is supported on the Intel and AMD 64-bit processor families. ArcGIS Server is a native 32-bit application. It is certified to run as a 32-bit application on 64-bit (x64) Microsoft Windows. Instructions provided below describe how to run the Internet Information Services (IIS) and ASP.NET 2.0 in 32-bit mode.  ArcGIS Server requires IIS and ASP.NET 2.0 to run in 32-bit mode.

Configuring IIS to run in 32-bit mode

Run IIS in 32-bit mode and install the 32-bit version of ASP.NET 2.0. Detailed instructions are available from Microsoft at the following link: Running IIS in 32-bit mode

IIS does not support running both 32-bit and 64-bit modes at the same time on a 64-bit version of Windows. Because ArcGIS Server for the Microsoft .NET Framework requires IIS and ASP.NET to run in 32-bit mode, other applications that require being run in 64-bit mode cannot be applied to the same server. For example, running IIS/Tomcat using the 64-bit isapi_redirect.dll on a 64-bit server cannot coexist on the same 64-bit server as ArcGIS Server for the Microsoft .NET Framework, since the isapi_redirect.dll requires to be run in 64-bit mode. More information on this limitation is available from Microsoft: Switching between the 32-bit versions of ASP.NET 1.1 and the 64-bit version of ASP.NET 2.0

Configuring ASP.NET 2.0 to run in 32-bit mode

1. Click Start > Run. Type 'cmd' and click OK.

2. Type the following command to enable the 32-bit mode:   

cscript %SYSTEMDRIVE%\inetpub\adminscripts\adsutil.vbs SET W3SVC/AppPools/Enable32bitAppOnWin64 1  

1. Type the following command to install the version of ASP.NET 2.0 (32-bit) and to install the script maps at the IIS root and under:   

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

1. Make sure that the status of ASP.NET version 2.0.50727 (32-bit) is set to 'Allowed' in the Web service extension list in Internet Information Services Manager.

ArcGIS Server for Microsoft .Net Framework is a native 32-bit application. It is certified to run as a 32-bit application on 64-bit (x64) Microsoft Windows. Web server support is based on the Web server vendor’s support of 64-bit Microsoft Windows. Check with a Web server vendor, if the Web server is supported on 64-bit Microsoft Windows.