No, it's simply a license that I bought. Likewise, with the GPL, there is no contract. The GPL is simply that which allows me to use another's coyprighted work where before there was no allowance. The Windows XP license has terms in it that would likely be declared invalid if the license were interpreted as a contract.
The agreement to buy that license is a contract. You agree to pay money, they agree to give you a license. I'm really not quite sure what you gain by denying this, but you're completely wrong in asserting that contract doesn't enter in anywhere.