You can use any Windows disk to reinstall but you will have to grab some alienware wallpapers just google it. You can theme it out your self better than they did with a little effort. You can even change your log in back ground here..http://www.julien-manici.com/windows_7_logon_background_changer/
I have used it for years and its free (just click the bottom GREEN button) the others are adds..Good luck getting it the way you want.
Its my understanding that the machines these days don't come with a COA like back in the day, rather, an OEM OS disk that's tied to the mother board of a specific model. If you are still under warranty, you can get them to send you an OS recovery disc, just contact AW support. If you're out of warranty, I'm afraid you'll be paying a premium for it.