What is the maximum number of parameters I can pass using the SQL IN clause in SQL server 2008 and SQL server 2000?
There isn't a quantity limit on the number of items in the IN clause.  The only limit is that the entire batch cannot be more than the batch size maximum.  In SQL 2008, this is 65,536 * Network Packet Size. In SQL 2000, I'm not sure if the limit was smaller than that.

This link describes these limits for 2008