Couple of questions before any conclusion:
a. Have you downloaded Tableau Desktop 10.1 and tried to install on your laptop which has windows 10 ? Tableau provide a free trial for 14 days, so you should not be stuck as they will provide you 14 days time to enter the key
b. One key is for one person
c. If your key is already in use they get a new key key.
d. While applying key, if you are on Internet then the activation process is simple, else offline activation process to follow which is little complex.