Aplications dvd problem

Call AppleCare, and ask for a replacement DVD. If this fails, bring it in for service to have the optical drive cleaned if it is under AppleCare. If it is not, you may want to try a slot loading DVD cleaner. If that doesn't work, you may need to get the drive replaced, or buy an external one known to work with Macs from http://www.macsales.com/

It is not that easy. My advice is to:

1. Backup at least your Home folder, and perhaps whole disk, to an external disk or DVD with, for example, Carbon Copy Cloner
2. If you have a Lion DVD from which you can boot and reformat your drive then do that
3. Boot from Snow Leopard DVD and reformat (erase) drive - will do no harm to do it twice
4. Install Snow Leopard and do not import any settings or Applications from Lion

For further details you can do a Google search or see: http://www.pcmag.com/article2/0,2817,2389334,00.asp

Good luck.

Have you now resolved your problem?

I am glad you have resolved it.