A prepared statement is not the equivalent of a stored procedure, as a SP has an execution plan (the servers choice of the 'best' method of running the SQL). A prepared statment (AFAIK) just basically says 'the syntax is valid, so dont bother checking'. However, for a straight Insert as you have this isn't really an issue.

One better method for inserting lots of records is to do a Bulk Insert. I haven't done this myself, but there should be a decent explanation in Books Online or the ADO help files (or from another forum member!).

Another option is to use the Import facilities of SQL Server, I believe there is a utility called BCP which does this, or you can use the "Import data" wizard in Enterprise Manager to set up a task to do it (this task can be scheduled later).