To retain 4.50, you would need a copy of the full PUP file (not the smaller one (e.g. 300mb vs 800mb)).
If you want more than 2TB, you may want to look at a 3.5" kit as the 4TB 2.5" may have height issues (assuming they're compatible).
Cheapest way to upgrade may be to buy a 'portable drive', just make sure that the USB controller isn't built in (I know Seagate and WD 1TB's have done this, but Seagates 2TB portables (so far) haven't).
edit:
That said, I'm not sure about the DRM.
why not just plug in an external drive? way less trouble.