Sometimes it is necessary to generate a set of ids for new items to be imported. One way to do this is with the "nash" tool, located at http://{server}/{application}/Client/scripts/nash.aspx (e.g. http://localhost/InnovatorServer/Client/scripts/nash.aspx).
1) Set the User, Password and Database fields and click the Login button.
2) Set the Action field to generateNewGUIDEx and the XML field to <Item quantity="x"/>, where x is the number of ids to generate.
3) Click the Submit button. You should get a semicolon-delimited list of ids in the response.