Well basically, the manufacturers distribute laptops to the retailers with operating systems preinstalled which have information built in them to allow them to be pre-activated on arrival so that customers do not have to worry about activating there operating systems or bothering manufacturers tech support departments.
This is the norm when buying a laptop from a retailer, there normally already activated from the warehouse.
So yes all's you need is the manufacturers Vista activation files and you can more or less activate any version of windows vista you have installed as long as the manufacturers activation files relate to your model of laptop / desktop. Again updates are 100% available.
I do not condone this though, and yes its josh posting as guest.

Hope this helps.