Uh I hate to throw a spanner in the works here, you sure UAC is the answer?
Only reason I say, after browsing through these posts notice it's a little different to my experiences.
Running vista, I have RTW, BI and EB installed without being in a user folder (C:\Games\RTW\ to be precise). I have UAC on , but have never had to give RTW admin priveledges, run in compatibility or anything. What's more I also have XP 64 installed too and EB runs perfectly happily in that just by launching from the direct from the same exe.
Of course I might just be lucky :)
Oh and by the way, you're better off going back to XP or at least dual booting, DX10 is an absolute waste of time right now
Cheers