I recently struggled installing and configuring OBIEE 10.1.3.4 on Windows 2008 64 bit OS. I got the infamous HTTP 500 error. OBIEE 10.1.3.4 is NOT supported on Windows 64 bit OS but you can try the following steps to try and get it to work. Note, ideally you want to avoid 64 bit compatibility issues if possible by taking the 32-bit route. I am documenting a couple of steps that seemed to be the key in solving my problem.
Installation – When you run the setup, you might be welcomed with the incompatibility message below. Try running the setup.exe in Windows 2003 compatibility mode. This worked for me and the installation went through.
Configuration – Before you start configuring OBIEE Plugin on IIS Server, you need to run the following command:
C:\inetpub\adminscripts>%windir%\system32\inetsrv\appcmd set config -section:applicationPools -applicationPoolDefaults.enable32BitAppOnWin64:true
The above command enables 32 bit app on 64 bit OS. Without setting this option, I got HTTP Error 500.0.
You may need to search adsutil.vbs on your Windows server. Once you find it you can copy it under C:\inetpub\adminscripts or where ever you have inetpub on your PC.
Another command that I have seen people use is below, but It did NOT work for me.
C:\inetpub\adminscripts>cscript adsutil.vbs SET W3SVC/AppPools /Enable32BitAppOnWin64 1
Microsoft (R) Windows Script Host Version 5.8
Copyright (C) Microsoft Corporation. All rights reserved.
ErrNumber: -2147221020 (0x800401E4)
Error Trying To Get the Object: W3SVC
Good Luck! 
