I have a toshiba satelite A60 Laptop and have had trouble trying to burn AVI files to a blank DVD Disk, each time i place a disk in the machine, it tells me that there is no disc in there. I have been able to record music to a normal cd without problems. Anyway after trying to fix this myself i went into the registry and accidently deleted some files, i think i deleted something to do with the DVD/CD drive as it is now not recognising blank cd's or any media whatsoever.

What DVD software do you have? XP does not have the capability within itself to burn or play DVD's.

As to your changes try a System Restore to a point prior to the problem:

start > All Programs > Accessories > System Tools > System Restore