Calling them wont help you because they cant verify you own the copy. One quick question just to make sure, did you physically buy it or buy it digitally, it sounds like you physically bought it but just making sure. If you bought it digitally go to where you bought it and the CD key should be saved.
Your only really option are key finder software programs
http://www.magicaljellybean.com/keyfinder/ is one that a friend of mine uses (yes you have to buy it but its a lot less than another copy of windows, and then there is
http://recover-keys.com/ which I bought over Jelly Bean (I honestly can't remember why).
There are advantages to having them because they scan your registry and pull a ton of cd keys for you. I keep a copy of it in a few different places that way I always have them.
EDIT: So I decided just now to reinstall recover keys and it is no longer accepting my registration key, I went to cnet and saw other ppl with the same issue so I would go with jelly bean if you go that route.
