This smells like the old upgrade problems
One program installs a filter driver that works fine on XP
Vista gets installed and breaks the program that uses the filter driver
Vista does not know how to remove the filter so keeps it in but it will not work as its not vista compliant.
Because the filter is not working Vista looses connction with the DVD drive.
With any change of O/S I always recomend a clean install, this way you reduce the problems that can be found doing an upgrade.
I use Vista and find it alot more stable and reliable than XP, even in its current form. Some programs are still having problems but most of the ones I use every day are fully compliant and I have yet to have it crash on me.