Thank you for your help.
But i have already tried all the solutions i have found here, I read and tried all your suggestions.
This is my problem: i have installed a program named driver detective, beacuse i was trying to search an update for my video card's driver.
After installation i run the scan and the program showed a lot of non updated drivers. So i have installed the updates, i know, this was a mistake because i forgot to read the updates characteristics.
One of them "wdm_A398" has been suggested by driver detective, to update audio, video and games controller.
After this my dvd-rom became unavailable. My OS does't read the cd-dvd rom.
And if i try to delete the driver (in the Device Manager, the drive with the question mark on, as indicated by a post of yours, when i try to re-install it, i recieve an error message, saying that there was an error during installation, the driver could not work... etc.)
And I can't find the way to delete the new update...
I hope to have written in a clear English, because I'm Italian and my English is not so good.
Thank you for your help, anyway.