I am just seeing your post but the SQL Server 2008 binaries are AnyCPU that is it can install as both x86 and x64 and you don't need to install x86 to use x86 ODBC drivers because both are in all x64 operating systems. And you should be able to access your ACE driver through the x86 ODBC.
I did not say there are x64 ACE drivers I rather said you can use the x86 ODBC driver in the WOW64 directory of your x64 Vista to load on the x86 directory of your x64 SQL Server 2008. That is the application must build x86, you only get issues when you try to load it as x64 or AnyCPU if you are in managed code. So I am trying to save you the extra hop to the x86 SQL Server because everything x64 in the Microsoft platform also loads the x86 version of that dll.
Kind regards,
Gift Peddie