This is where your computer stores everything. The information written to the Hard Drive stays there, even when the computer is powered off. It does this by having magnetic platters upon which information is stored. These platters spin while a sensor reads the data, much like a record player reads a vinyl album.
Hard Drive storage boils down to 2 major things: Capacity and Speed.
Capacity is how much storage space you have. Video, Music and extremely large picture files are the biggest files that most people use. This storage space is measured in Gigabytes, and drives sizes are fast approaching the Terabyte mark (that's 1000 Gigabytes!)
Speed is how quickly the hard drive accesses your stored files. On a fast hard drive, Windows boots faster and you can play, move, load, edit and delete files quicky as well. Hard drives speed is measured by the number of "revolutions per minute", or RPM. Again, to think of your hard drive like a record: The faster you turn it, the more music you can play in the same period of time!
There are different ways that hard drives connect to your motherboard. You might have heard the terms: IDE, SATA, or SCSI. I've found that SATA hard drives are ideal for 99% of our customers, and give the best performance for their price.
There are several types of interfaces that hard drives use. For the last decade, almost all hard drives were ATA (Advanced Technology Attachment) format. Now that Serial ATA (SATA) has become the new dominant format, ATA has been retroactively renamed "Parallel ATA" or "PATA". This format has bandwidth transfer limitations (see below).
What the heck do you mean "hard drive bandwith"?
The hard drive communicates with your motherboard, sending data back and forth between the two. This data is communicated by a cable which could be visualized like a big pipe. Older interfaces, like PATA, are a smaller pipe, and fills up faster. If you try and move too much stuff down the pipe at one time, it'll back up at one end!
Newer interfaces have a bigger pipe, which let you move more information without getting all stoppered up!
The SATA format has become the new industry standard for hard drives. The transfer rate is vastly increased over ATA, allowing for faster hard drives and longer cables. In addition, SATA has support for better internal connections, which allow for "hot-swapping" and other features which PATA was unable to support.
"SCSI" is another format that has been around for a long time. While SCSI drives are still very fast and very stable, they're also extremely expensive. When compared to SATA 10,000 RPM hard drives, you get about a 30% performance increase, but you end up paying nearly 300% the price.
The industry is looking to move past these rotational hard drive models, to a solid-state disk which involves no moving parts. While these drives look promising for the future, they're currently still slower and very expensive.
Hard Drive pricing is certainly not linear. You might find that an 80gb hard drive is only $5 less expensive than a 160gb model. I typically recommend that you look for the "sweet spot", where you're getting the most bang for your buck. If you have exceptional storage space needs, you might need to consider the larger, but far more expensive models. Faster hard drives also tend to be smaller, and more expensive. Currently, 10,000rpm hard drives come up to 150gb, while 7,200rpm drives go all the way up to 750gb!
It's often not easy to estimate your future storage needs. Typically, most users would take years to acquire over 100gb of data. However, a power user who deals with many installed programs or a media enthusiast who collects volumes of music and video might find himself running out of room quickly.
If you're after speed, a 10,000rpm hard drive is a great solution. The 150gb model is expensive, but gives terrific performance with plenty of storage space for the average user.
Keep in mind that most computers can support 4 or more hard drives, so if you need to expand in the future, you usually have options. Fairly new to the market are external hard drives that connect to your computer via USB or Firewire. One of these lets you easily store your infrequently accessed files, and also gives you a great method of redundant storage for backing up your data. These external drives can store hundreds of gigabytes of data, making them the easiest and largest portable data storage available.
Many users want both speed and capacity, in which case multiple hard drives are a terrific solution. By using a 10,000rpm as your "primary drive", you can install your operating system and programs onto this smaller drive to take advantage of the high speed, but you can still have a very large "secondary drive" for storing all your large data files.
A lot of hype has been given recently to 'RAID Arrays', which is a complex method of combining hard drives to increase either speed or redundancy. It's my opinion that a RAID array is almost never the ideal solution. The performance increasing RAID setups are doubling your chances of a hard drive failure that destroys all your data, while giving an extremely marginal performance increase. The redundancy-based arrays are great for protecting your data from hardware failure, but don't remove the need for proper data backup as it gives no protection against a virus or accidental file deletion.
When configuring systems, I consider 10,000rpm hard drives a luxury. If you can afford one, you'll love it. However, if it falls outside your budget, I wouldn't let it worry you, you can still get a fast, strong system.
Most importantly, purchase from a well known company and check on the warranty offered by that hard drive manufacturer. The best manufacturers are offering up to 5-year warranties on all their hard drives. You can never go wrong with a good manufacturer warranty.