they are not the same. the first Beta was Office12 Beta, the next one was Office 2007 Beta1, next was Beta2 and the last one was the TR of Beta2. This was a great update with a lot of bugfixes and improvements.
Windows XP x64 use the same codebase as Windows Server 2003 and also shares the same versionnumber NT 5.2. If a program can't detect XP x64 seperately it thinks you use a server OS. The only thing you can do is, to update the software and hope that x64 is supported
this works only with a trick. You must set a reg-key and Windows think now Setup is ready. This Key is needed to install .NET 2.0. Check http://aris-toolz.de/dotnet2.html and see how Ari made this