How to find "outer join in the where" syntax in SQL 2005 using cmptlevel 80?
A quick search of StackOverflow would show you use sys.sql_modules or OBJECT_DEFINITION to search for code on SQL Server 2005+. You can simply restore onto SQL Server 2005+ but not run to allow this.

That's if you want fool proof T-SQL. You could concatenate the syscomments rows together if you wish though in SQL Server 2000. I wouldn't personally.

Alternatively, use the SQL Server 2008 upgrade advisor to pick out most (maybe all) possible issues (such as ambiguous ORDER BY clauses which caught me out).

Note the Red Gate SQL Search sensibly only supports SQL Server 2005+