Getting a bigger HD - problems ahead with authenticating ?

I've had problems in the past with authenticating my Vista Premium - and it
IS genuine by the way - every time I've had a problem and have had to
reinstall. The first time was the worst. 45 minutes on the bloody phone, and
even then I had to be given a new set of numbers. And three times since, and
I've had to go through the step by step business, because it wont
authenticate first time.
So - I am considering getting a 750gb HD to replace my 200 and use THAT as
main drive. Will I be forced into yet another 45 minute phone call to India
?