FogBugz 6.x will work fine on Windows 2008.  The only things you need to do are

1. Install IIS 7 (it doesn't come preinstalled) and check off the boxes for .NET/ASP/CGI/etc
   
   
   
2. Disable DEP by typing "bcdedit.exe /set {current} nx AlwaysOff" on a command prompt. And then make sure you reboot afterwards.