Installing Nightfall problems

I just purchased Nightfall and it's already giving me problems, before I've even started. I went to install and got up to "Put in disk two" For some reason, my computer wouldn't read it. Won't read Disk one now as well, but other disks still work (Factions does at least.)

There is no visable scratches or anything on the disks and I did use my disk cleaner just in case, but still nothing. Is this a common nightfall disk problem or what?

You don't need the discs. Download the client from http://www.guildwars.com/support/downloadclient/ and just enter the Nightfall access key. Just click on the "Play the Game" logo at the bottom of the page.

EDIT: I see you already have Factions installed, just add the Nightfall key to your existing account.

THANK YOU! I was afraid I wasted my money. I can't return it to the store as the store is going out of business.