On a 64-bit version of Windows Server 2003 that has SP1 installed, IIS starts a 32-bit worker process or a 64-bit worker process, according to the value in the following metabase property:
When the value for the Enable32bitAppOnWin64
property is 0, or when the property is missing, IIS 6.0 starts a 64-bit worker process. If the Enable32bitAppOnWin64
property is present and the value is anything other than 0, IIS 6.0 will start a 32-bit worker process.
IIS 6.0 cannot make sure that configured ISAPI Filter DLLs and ISAPI Extension DLLs can actually load in a worker process. You must make sure that only 32-bit ISAPI DLLs are configured to load in a 32-bit worker process or only 64-bit ISAPI DLLs are configured to load in a 64-bit worker process.
If you configure a 32-bit ISAPI Filter DLL to load in a 64-bit worker process or if you configure a 64-bit ISAPI Filter DLL to load in a 32-bit worker process, an error message that is similar to the following may be written to the Application log:
Could not load all ISAPI filters for site/service. Therefore startup aborted.
Data: 0000: c1 00 00 00
If you configure a 32-bit ISAPI Extension DLL to load in a 64-bit worker process or if you configure a 64-bit ISAPI Extension DLL to load in a 32-bit worker process, you may also receive a 500 error response that contains the following text:
%1 is not a valid Win32 application
We also recommend that you use a 32-bit debugger to troubleshoot 32-bit Web applications. Or, use a 64-bit debugger to troubleshoot 64-bit Web applications. The dump file information may not be accurate if you use either of the following methods:
- You use a 64-bit debugger to debug a 32-bit process or application.
- You use a 32-bit debugger to debug a 64-bit process or application.