Symptoms
Windows Shared Hosting Websites return Service Unavailable
error on any page.
Cause
The source of this problem is IIS, which works in 64-bit mode by default. The problems related to IIS functionality in 64-bit mode are described in the following article:
http://support.microsoft.com/?id=895976
IIS 6.0 supports both the 32-bit mode and the 64-bit mode. However, IIS 6.0 does not support running both modes at the same time on a 64-bit version of Windows.
Resolution
To switch IIS to 32-bit mode, the following command should be used:
cscript %SYSTEMDRIVE%\inetpub\adminscripts\adsutil.vbs SET W3SVC/AppPools/Enable32bitAppOnWin64 1
2.To switch IIS back to 64-bit mode, the following command should be used:
cscript %SYSTEMDRIVE%\inetpub\adminscripts\adsutil.vbs SET W3SVC/AppPools/Enable32bitAppOnWin64 0