Why not get a fresh copy from
Microsoft SQL Server Community Projects & Samples[
^]
Anyhow the error is a bit confusing. You try to attach primary file
AdventureWorks2008R2_Data.mdf
but the error message implies that SQL Server cannot find file
TestDb_log.LDF
. That doesn't seem the be the default log file of the AdventureWorks database. Are you actually trying to attach a mdf file that is already in use by Sql Server?