Did you just get a brand new DVR/NVR or you already have one and you're looking for a larger capacity drive tailored for such use? If the answer is yes then you should really consider getting the brand new Guardian Series Skyhawk 10TB model by Seagate.
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips