Do I need to install anything special to allow sql server 2008 express to run on a windows 7 64 bit os?
You must have installed .NET 3.5 SP1 it also helps if you are running VS2008 with SP1 installed. Then you also need the correct binary because there is one version for VS2010 beta testing. So check links below and download the SQL Server 2008 Express x64 and x64 SP1.