Thunder Pants, I love the name by the way, if you ever registered your serial key's at the nwn.bioware.com site then you shouldn't have to repurchase the disks for anything other than installation. If your lucky enough, mabey you can find someone in your area to loan you the disk so that you can install and use your serial keys.
I know I've lost my serial key papers time and again and have always been thankful that bioware lets me copy and paste it from the website.
Good luck mate.
go gamer has the gold version for 20$
All PC Games - Neverwinter Nights Gold
And you can find the diamond version at target/gamestop for 20 bucks also (includes both expansions).