how can i fix my son video now disc?

You can try:
1. wiping with a soft dry cloth;
2. wiping with a cloth and ethyl alcohol (or just use a CD/DVD cleaner kit);
3. polish with an alcohol-based furniture polish and then use the CD/DVD cleaner to ensure no residues;
or
4. Throw it out and replace it (sorry, but this is probably the only realistic option).

Ken
January 2005