Before I start telling you what the best internal hard drive out there is, I'd like to take just a few sentences to talk to you about storage capacity. 1 Terabyte. If you'll recall from your high school chemistry days, the SI prefix scale goes deca-, hecto-, kilo-, mega-, giga- and finally tera-. One terabyte is effectively one trillion bytes. That's a lot of information, so much information that you could store 1 billion movies on the drive, or a quarter million full-length videogames, or a quarter trillion songs. So, when I tell you about the best HDD out there, it has to have at least 1 terabyte of storage (and if we were talking external drives, buy.com was driving a hot deal on a 2 Tb external hard drive).
So, who wins out?
The Western Digital Caviar Black WD1001FALS
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136284
Western Digital makes an amazing product, and their line of hard drives never fails to impress. Be it the high spin speed or the amazingly good read rates, you can't help but feel right at home with one of their drives. The WD1001 particularly impresses though with its wide array of technological advancements.
First of all, the HDD has a huge 32 Mb cache - which makes it increasingly easier to pull files from the hard drive for use in the RAM. Add to that the dual-processing capabilities of the drive, and you have one fast HDD.
Furthermore, new StableTrac system technology make the magnetic reader/writer able to more stably read the information stored on the disk, making for less errors while reading and taking less time to read back the information. Adding to this stability is the fact that WD is employing some new technology to make sure that the reading and writing head of the HDD never actually touches the disk. This ensures stability in a way that no other drive before it has, making it a great working HDD even in motion.
Compound to that the HDD's amazing 1 Tb storage (in a single drive, mind you), and it's ability to work off SATA and read/write at 3 Gbps, and you have yourself the winning hard drive. Now, other competitors may offer you different programs that will protect your information, but only the WD program has ever worked successfully for me. The Lifeguard program works well and has a great user interface.
Overall, the product is a winner in every category, and at $120, the price is not too bad. I'm sure you could probably find cheaper drives, but you won't find one with this many different features.