Not sure if it's available for download, except possibly as part of the trial version of SQL Server. If it's not included in one of the SQL Express packages, it's not available.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
We stand on the bridge and no one may pass