Missing TrayApp

Computer is an HP Media Center M480n Windows XP SP2. Slow dtartup so I cleaned my Registry Bad mistake, now when i start XP I get Windows Installer Preparing to install "Please wait while Windows configures ArayApp" This is followed by "feature you are trying to use is on a CD-ROM or other disk that is not available" Insert 'TrayApp' and click OK Use Source 1
No such animal. Computer then hangs till Ctrl-Alt-Del is used to end program. If closed, Error 1706 is displayed. In addition Media Center is cooked as well. For FM I get Tuner not found error and for TV I gea a Video Error. HP Image zone is also messed up.

Don't want to completely restore if possible because I may lose some of my installed software (1clickDVD for example) Have ordered restore disk from HP as well as upgrade to Media Center 2005. System will not back to an earlier date as well. Any ideas short of starting all over? Thanks, an unrated geek.