Installing Snow Leopard from disc: click install, nothing happens!

Hello,

I recently purchased the Mac OS X Snow Leopard 10.6.3 disc to update my iMac from Leopard 10.5.8.

I checked all of the prerequisites and think my computer meets all the necessary requirements for the upgrade.

After inserting the disc, the Installation window pops up, I clicked continue, it recognized my hard drive and I clicked install. The prompt comes up "are you sure you want to install Mac OS X? Click install to quit all open applications and install Mac OS X Snow Leopard on Macintosh HD. " The options are to cancel or install. I click install and then nothing happens.

Ive tried it a few times now, even restarted my compuer... There are no other prompts telling me theres a problem, just nothing more happens.

If anyone has any insight I would truly appreciate it because Id like to get up to speed with the new operating stystems.

Thank ou!!!