When browsing to a SharePoint 2010 site, the following error occurs: “HTTP Error 503. The service is unavailable.”
You may also see this event in the Application Event log:
Log Name: Application Source: Microsoft-Windows-IIS-W3SVC-WP Event ID: 2282 Task Category: None Level: Error Keywords: Classic Description: The Module DLL 'C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\isapi\owssvr.dll' could not be loaded due to a configuration problem. The current configuration only supports loading images built for a x86 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 http://go.microsoft.com/fwlink/?LinkId=29349.
The IIS Web Application setting "Enable 32-bit applications" has been set to True. This setting will not allow a SharePoint 2010 IIS Web Application to load due to a processor architecture configuration mismatch.
You can correct this problem by turning off the "Enable 32-Bit Applications" setting for the SharePoint application pool. 1. Click Start, click Run, type inetmgr, and click OK. 2. Click on Application Pools, then click on the application pool you wish to change. 3. Click on Advanced Settings in the Actions pane. 4. Change "Enable 32-Bit Applications" setting under the General section to "False." 5. Click OK. This will trigger and Application Pool restart.
If a SharePoint 2010 hosted application requires 32-Bit Applications enabled, it is recommended to move the application to its own IIS Web Application.