Yeh,ran that Diagnostics test,everything fine.Downloaded version 9.0.1 of iTunes and am using a Dell computer.Searched internet for help,no luck.Downloaded Nero but,excuse my ignorance, I dont know how to use it!!
(From Apple support Website)
http://www.gearsoftware.com/support/drivers.php
I went to the middle of the page and clicked on driver downloads and downloaded and save the first option.
Once you install the driver, I would re-start the computer, then try to open i-Tunes to see if you still get that annoying message. If you do, un-install everything that has to do with i-Tunes and Quick time. Make sure you un-istall anything and everthing that has to do with these two programs. Re-install iTunes, re-start, and hopefully when you start i-Tunes up again the message will be gone. Also, when you go to burn a disk, you might get a error message at the end, if you do, change the burn time to a lower time. I think it is set for the fastest burn time and that can cause an issue also.
I hope this helps. It sure did help me. I can not say enough about this guy, he was so helpful.