3. Comparing the time of your initial install and the later occasion when you had to enter the key again... has the laptop been connected to different networks at these two times?
4. Please open WIndows Explorer and type %APPDATA% (press return) in the address bar; then report the path you were taken to.
Just to make sure, you are not using a "roaming user profile"? This typically be if you're connecting on a company network, so probably not, but it's my only idea...
Also, after the second time, were you asked for the key yet again?
One more idea: do you have separate user and admin accounts?
If you do, than that's it, you won't be asked again. You get asked for the key once per user. That "feature" comes because the system is portable (windows, mac) so not perfect. You are free to enter the same key of course.