No disk in device??

XPS420 4gb ram  320gb hd   Q6600 quad      Windows Vista Home Premium.       DVD Rom went bad.   Replaced with a new one.   Put in DVD to see if DVD player worked.   Worked ok.   Stopped dvd and removed disk.    Now, after bootup,  a window appears stating that there is no disk in the device (meaning dvd rom).   I can cancel the window, but when I open the mailbox for instance, the window reappears and I must cancel it to get into the mailbox.  This continues every time I open the mail.   I tried removing the dvd rom, but it still does this.   However, if after the inititial screen comes up, I put any cd in the drive and after it recognizes it, I can cancel it and everything works ok for the rest of the session.  I can even remove this disk and the computer still operates normally.     But, next time i boot the same thing happens.    Any ideas how to get rid of this annoyance?