my first test to get a given database with activated fulltextsearch running on a sql2008 failed with the result that it creeps. sql2008 took several the time of sql2000, but why?
The full text engines in SQL 2000 and SQL 2008 are totally different.
In SQL 2000 when you submit a full text query to the database, it searches the entire full text index and returns all matching rows to the full text query back, and then filters those down against the rows returned by your query using the normal filtering that you supplied as table filters.
In SQL 2008, then table filters are applied first, then those rowIds are sent to the full text search, and the full text search is run against the rows which matched the table search.
You may need to rewrite your query to improve query performance on the different version.
Also in SQL 2008 the full text index is stored within a SQL data file and the search is performed by the SQL Server Engine. In SQL Server 2000 the full text index is stored outside of the database files, and the searching of the index is processed by the Indexing server.
For some further information you can see Brent's experiences with the differences and how the affected StackOverflow here