This is different from the privileges offers of Credit Card companies. Credit Card companies do not specific the valid period of the privileges provided to the cardholders. Therefore they will have to inform their customers if they make any changes on their offers.
The Vista Express Program is a Limited Time Offer. The details of the program are listed clearly in relevant websites.
In the DM of the laptops, you can see the line “Visit www.xxxxxx.com for more details about the program”
I do think it is your own reasonability to understand how the program could apply to you before you make a decision of purchase.
Speaking of E-mail, did you allow HP to send you e-news e-mail?
The New Flying MacBook Pro; Seatbelts sold Separately!