Help Windows KEY

[Lolcb]

Hi, I bought an OEM windows xp home ages ago, now I lost the sticker that consist the 16 digit unique keys.

I take it that I have to purchase a new one, and atm I really need this OS installed, and I know that you can buy the key off MS. Can someone show me the URL please?

 

[Lolcb]

http://www.snapfiles.com/get/rockxp.html

How do you use that when you don't have the OS installed? Any ideas??