Nothing to do with SQL Express.
You have a SQL 2008 R2 backup that you're trying to restore to a SQL 2008 instance (not R2). They're two different versions and you can never restore down-version. You can restore up-version or between editions on the same version, but not down-version.
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