ColdFusion 8 is a 32 bit application and by default won’t run on IIS6 on Windows Server 2003 x64. You’ll get a “%1 is not a valid Win32 application” if you try.
To get IIS6 to run 32 bit applications (including classic ASP) you need open a dos prompt and type:
cd %systemdrive%\Inetpub\AdminScripts cscript.exe adsutil.vbs set W3SVC/AppPools/Enable32BitAppOnWin64 True IISreset.exe /restart
Try to view a static html page, if you get a “Service Unavailable” error (like I did), then the quickest way to solve it is to remove IIS (from the control panel), reboot and reinstall IIS. WARNING: you will need the windows install files to do this!
Now, you can go ahead and install ColdFusion 8.
now musing at www.aliaspooryorik.com! 
Thanks so much for this article! I’ve been beating my head against the desk trying to figure this out.
you seriously saved me HOURS from having to deal with Adobe’s HORRIBLE customer service…thank you so much!!!
Glad it helped Matt. It’s one of those things that is easy when you know how!
Thank you for this fix, it has saved me many more hours of searching for a fix and failing.
You are my hero! 1000x thanks
As above -thanks! Even guessing that it was the 64-bit install at the core it would have taken me forever to figure out that fix.