Laptop doesn't recognize dvd

[Me Llamo Hefe]

I've got a Dell Inspiron. If I turn the laptop on with a dvd in the dvdrw, it will recognize the disc in there and let me access it. If I open the drive and put another disc in, windows doesn't even acknowledge that there is a dvd drive. Windows explorer and Nero both say that the drive doesn't exist. The only way for me to recognize another dvd is to restart the computer with the disc in the drive.

Does anyone know why it does this or how to fix it?

Thanks