A similar loss of DVD-reading happened to me when removing the Adaptec
CD-writing software from a computer being upgraded to Vista. DVD-reading
was restored by some combination of allowing Windows to update driver
software, adding in some drivers I had saved beforehand and rebooting,
allowing me to continue with the Vista upgrade.
CD-writing programs are a good reason for doing a clean install of Vista
instead of doing an upgrade install. Typically the CD-writing software for
Windows XP is not suitable for Vista, but uninstalling the CD-writing
software in preparation for an upgrade to Vista can disable the DVD-reading
needed to do the Vista upgrade. When I installed Vista on a second computer
I did a clean install and did not remove the Nero CD / DVD software,
allowing the clean install to get rid of the old version of Nero (details of
the upgrade and its display and speaker problems are at
http://www.gottabemobile.com/forum/forum_posts.asp?TID=2129).