I dont see your problem. At all. You have to pay for the game regardless. And i definately dont see what diffirence it makes now that you already have done so.
But just to amuse you, you can update your game without even logging in, or making/registering an account, simply by removing one .DAT file, and selecting the File Check option. This will A: replace the file you removed, and B: start downloading the entire list of updates.
Still, if out of the 30 free days, you have to spend at the very most between 2 and 4 hours downloading files, what kind of a loss would that be? They implemented a lot of updates in the digital downloads. Just the latest ones from the last couple of months are missing. I did the same recently when i purchased a second account. It was absolutely painless.
Or are you by chance installing the game from CD's from 2003? In that case, why are you installing from such an old build in the first place?