How did you migrate them? Did you upgrade the database by restoring it from the old server to the server? Did you upgrade the old server to SQL 2005? Did you attach the database to a new machine running SQL 2005?
In all these cases the stored procedures are written exactly how they were when they were in the old system. The only task that must be performed after upgrading is that the statistics must be updated manually on the server as the SQL Server 2005 database engine can’t use the SQL Server 2000 statistics.