How to give application pool user permissions to launch and exit MS Word 2007?

IIS 6.0 Application pool user has to launch Microsoft word. we have given the pool user the permission to launch the  applicaion in  the DCOMCNFG. but the problem is that the application works fine when we give the Identity impersonation with the pool user credentials in web.config. But we need to to run througb the application pool not through impersonation how can we do it?

We have checked giving the administrator in the applicaiton pool user it works fine. but when given the other users with administrative privilages it doesn't work