When the installer for ArcGIS Server is run on Windows Server 2008 64-bit it does not enable 32-bit applications on IIS unless 'IIS 6 Scripting Tools' is installed from Windows Features. It does perform this step on Windows Server 2003 64-bit.
This defect is closed as non-reproducible as the steps/data needed to reproduce this issue are no longer available. If your client has a reproducible case on a supported configuration, please work with a Tech Assist to reopen and edit this defect.
解决办法
Install IIS 6 Scripting Tools before attempting to complete the installation of ArcGIS Server.