IRQ conflicts. dvd/cd rom doesn't work

I have a Dell Latitude D800, running xp pro. The DVD/CD combo drive sometimes does not show. Other times it will not play audio cd’s. when the drive doesn’t show i check it in device manager and it shows an IRQ conflict with COM port 1. However com port 1 is not hooked up to anything. does anyone have any suggestions? any info would be appreciated

Disable unused COM ports in the BIOS - or set to Auto