How to Buy a Hard Disk–Hard Drive Buyer’s Guide

If your computer seems slow and you’ve already upgraded your memory (say, to 2GB or higher), your next step might be to upgrade the hard disk. First, check out your current hard disk’s performance using HD Tune. Write down the average transfer rate and access times so you’ll know how much better your new disk is. If you’re running Windows Vista or Windows 7, you can use the Windows Experience Index to get a rough estimate of your disk speed.

Now, figure out what type of disk you want to buy. Write down your choices as you go:

  • Internal or external. If you want to improve system performance, you’ll need to replace your system disk, which means you’ll want to buy an internal drive. They’re more work to install, but they’re cheaper and faster. If you just want to add a second disk for backup or more capacity, go external.
  • Physical size. If you have a laptop, you probably need a 2.5 inch drive. If you have a desktop, you’ll want a 3.5 inch drive.
  • Interface. Nowadays, most computers use Serial ATA (SATA). If you want an external drive (which will save you from having to open your computer’s case), use external Serial ATA (eSATA) if your computer has it. If not, use Firewire (if you have it). As a last resort, you can use the USB interface. Your disk will be slow, though. If you choose Firewire (IEEE 1394) or USB, buy a disk with low RPMs, because you’ll save money and electricity, and the performance difference won’t much matter. This picture shows internal SATA (in red) and external SATA (in black):

Now that you’ve written down your choices, do a search at or For example, you could search for “3.5 inch external serial ata” or “2.5 inch internal serial ata”. You’ll see many different models, with varying speeds and capacities. Consider these points:

  • Speed. For conventional drives, the most important metric is revolutions per minute (RPM). Typically disks come in 4500, 5400, 7200, and 10000 RPMs. Faster is better, but uses more power.
  • Capacity. Bigger is better because you can store more stuff, of course. For conventional drives, bigger drives also improve performance–usually. For example, if you compare two 7200 RPM drives at 500GB and 1.5TB, the larger drive will probably be faster. You always need more disk space, so buy the biggest drive you can.
  • Solid-state or conventional. Super-expensive solid-state drives use flash memory instead of rotating magnetic media like a conventional disk. As I described here, they’re each fast in their own way. Conventional disks are still the best value for most people. Get a solid-state disk only if you’re a mobile user and you want to improve battery life or need durability (and you don’t mind Windows being a bit slower).

Here are some factors to ignore:

  • Brand. For home users, this doesn’t much matter. You’ll find people with horror stories about every brand of disk. So, disregard it.
  • Throughput. Drive manufacturers always list the maximum theoretical throughput of the disk, but it has no bearing on the drive’s actual performance. So, just disregard it.

Hard disks sometimes attempt to distinguish themselves based on power usage, noise level, reliability, and warranty. If power usage and noise level are important to you, find a disk that specializes in those areas. I generally dismiss reliability claims, because for home use, it doesn’t make much of a difference. Hard disk manufacturers have definitely cranked out some unreliable drives, but there’s no good way to know if a current model is going to be reliable. Nowadays, most drives are plenty reliable, but regardless, you’ll need an extra disk to make backups. I dismiss warranty, too, because by the time the hard disk dies, newer, better disks will be available for less, anyway.


Wait, don’t click buy yet! Double-check these things:

  • Does your computer support the interface?
  • Do you have a cable to connect the hard disk?
  • If the hard disk is internal, does your computer have an extra power connector? If not, buy a Y-adapter/power splitter.
  • If the hard disk is internal, do you have room in your computer to store it? if the storage big is bigger than 3.5″, be sure your disk includes mounting rails. OK, I admit it–my computer has a non-mounted hard disk floating free inside the case, but that’s a bad idea.
  • How are you going to back it up? If it’s worth saving, it’s worth backing up. Consider buying two drives so you know you have enough space for backups.
  • Solid state or conventional.
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About Tony Northrup

Tony Northrup, MVP, MCITP, MCPD, MCSE, MCTS, and CISSP, is a Windows consultant and author living in Waterford, Connecticut, in the United States. Tony started programming before Windows 1.0 was released, but has focused on Windows administration and development for the last fifteen years. He has written more than two dozen books covering Windows development, networking, and security. Among other titles, Tony is coauthor of the Windows 7 Resource Kit, the Windows Vista Resource Kit, and Windows Server 2008 Networking and Network Access Protection (NAP). When he's not writing, Tony enjoys photography, travel, and being awesome. Tony lives with his girlfriend, Chelsea, her daughter, Madelyn, and three dogs. You can learn more about Tony by visiting his personal website at and his photography portfolio at

3 thoughts on “How to Buy a Hard Disk–Hard Drive Buyer’s Guide

  1. Yes, I do have an External Hard Drive that I use to store all my information on. I had purchased a Seagate 320 GB external hard drive for that purpose, the storage of all my information. I do run a backup about 3 times per week so that this information is regularly updated.

  2. Recently bought a WD 2.0TB hard drive. I run Vista Business 32 bit. Having problems formatting the disc which seems to stop at 55%. Have I exceeded at maximum disc capacity for this system ?

    • No, Vista can format the entire 2TB (you’re using NTFS, correct?).

      Most likely, the problem is a flaw on the hard disk. I’ve had this happen before, and worked around it by creating three partitions: 54% of the disk, 2% of the disk (the portion containing the flaw) and the remaining portion of the disk. I then format the first and last partitions, and leave the partition containing the flaw unformatted.

      Seeing as how it’s a new disk, though, I’d just return it.

      Also, I’m jealous that you have one of the new 2TB disks :).

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