Either the fan is very dirty with dust, in which case you can try to open up the unit and clean the fan, but you have to be very careful during cleaning because if the fan is "spun" too fast it can cause damage to the fan. The other possibility is that the fan is already damaged, in which case replacement is the only option.
I am not sure what you mean by "registering" the unit with Shaw ... do you mean for them to "activate" it? Because from what I know, the only way for the unit to become functional in your house is to have Shaw "activate" it, otherwise you cannot watch what you have subscribed to, and in many cases you cannot even use the PVR functions of the unit unless they activate it. If it works without calling Shaw, then you are probably using the previous owner's account ... once Shaw realizes this (usually within a week) they will deactivate the unit.