Windows-Domain login without local users

hey freeRADIUS users, PEAP auth. works now with *X and MS-clients, the backend is a freeradius server on centOS with active directory connection. Now, the user needs a local account to login to the clientmachine and then he is able to start the PEAP authentication process. A local login for every user is a big overhead! What is the normal way to handle this? thanks ca mIke