about 3 weeks ago, i posted a problem i've had for many, many months after trying to upgrade my xp-home system to xp-professional. somewhere along the way, something was changed so that now my dvd/cd drive will not operate. no disc will load in or play. my system certifies that the drive is working properly. i even went as far as wiping out everything and reloaded my pc with its factory setting. i still have the problem. there is nothing wrong with the hardware. a friend placed the dvd/cd unit into one of his pc's and it worked fine. something has been changed in my pc that keeps me from being able to use my drive. can anyone help? -bill