• High Capacity USB Thumb Drives:
  USB Thumb Drives are now available in sizes as large as 64GB (soon to be even more).  While the USB interface is somewhat slow, these make an ideal solution for their small compact size.  Thumb drives are perfect for storing in files, or other compact spaces.  While their cost per GB is somewhat high, their convenience, USB interface, size, and extremely light weight, make them a very attractive option.
  
  Click Here for 32GB Thumb Drives or for 64GB+ Thumb Drives
   
• External Hard Drives
  Now you have a wide variety of options for external hard drives.  1TB (Terabyte) External Drives are now available for less than $200.00.  External drives come in a wide range of sizes, speeds, and interfaces.  They are available with USB (the slowest), Firewire (medium speed), and SATA/eSATA (the fastest). 
  
  When selecting an external drive, it is important to consider how you will use the drive, and the interface limitations of your computer.  If you have a laptop that only has USB ports, this would be your best (possibly only) option.  If you have USB & Firewire, get a drive that has Firewire for the performance boost.  If your system has a SATA or eSata port, get a drive with this option - it will give you true hard drive to hard drive performance. 
  
  However, also consider where you might need to restore the data.  USB is the most universal, in that almost all systems have USB ports.  If your system dies, and you need to restore your data, this may be your most important consideration.
  
  One last consideration is to keep your backup drive continuously connected, or only connect it during backups.  The general idea of backups is to have a copy of your data in case your system fails - which they do.  But you may also want secure protected backups in a safe or safe deposit box.  Regardless, external hard drives offer an outstanding solution for backing up your data, and the cost per GB is quite low.
  
  Click Here for External USB/Firewire Hard Drives
   
• Hard Drive Docks (Toasters)
  An incredibly simple, yet functional new product category emerged in 2008: Hard Drive Toasters (Hard Drive Docks).  This device lets you plug in regular internal hard drives as though they were pop-in flash drives.  You drop in your hard drive, and the dock instantly gives your system access to that drive, without wiring, or power connections - it's all done by the hard drive toaster.  This way you can use any compatible hard drive as an external removable hard drive for backup purposes!
  
  Click Here for Hard Drive Docks
   
• Online Backup
  Still another option is to use an online backup service.  These come in two forms:
  
       • Backup to another computer over the Internet
       • Backup to a central server using the Internet
  
  The first of these can work very well, and automatically backups when you are online.  The Microsoft OneCare service is one example.  It can backup your data from your system to another in your OneCare account across the Internet automatically, regardless of where you are.
  
  The second involves trusting your critical data to someone else's servers, and usually no real guarantee that your data will always be there.  If they loose your data, they just refund your fee.  This service may be fine for a couple of letters, but business critical data needs to be accessible forever.  For this reason, you are better advised to look to a hardware solution that you control.
   
• Backup Software
  Many products come with backup software included, such as External Hard Drives, and Antivirus products like CA Security Suite.  Most offer excellent features for automated backups.  But remember, backup software and devices, are only as good as your willingness to use them!  So backup regularly, and backup often.

1. The way size is calculated and displayed.
2. Any "Partitions" on the disk will change the total in a specific partition.
3. Hidden files and folders decrease available space.
4. Compression increases the apparent size, but not the physical size.
5. Drives larger than the OS or Drivers natively supports.

First, the definition of a megabytes (or gigabytes) is a unit of data storage capacity measured in 1,048,576 bytes (or 1024KB). The larger the numbers, the more apparent the size difference will be when listing the size as megabytes (or gigabytes) versus bytes. Actually, both numbers are correct. The noticeable difference is due to the 1024KB definition of a megabyte. This is why a 95.3GB hard drive can also be listed as having 102 billion bytes of total space.  Just think of it as "round off"  In the screen shot at right: The first number is the total number of bytes, the second number is based on the number of megabytes or gigabytes.

Second, some computers have a non-DOS hard drive partition that is used for features such as Save to Disk, Hibernation, or Recovery. This partition is not normally reported by the operating system, although it can be viewed using a disk partition utility.  This is very common on desktops and laptops.  NOTE: Partition information will be created or formatted automatically during initial system setup and a system recovery.

Third, by default, all system files are hidden and cannot be seen. This may adversely affect the reporting of available hard drive space. You can set your Folder Options so you view system and hidden files and folders, but do be careful as changes to system files can adversely affect your system.

Fourth, if you turn on Compression for a drive, it will increase reported free space and used space, but since compression is based upon the actual contents, this number is not fixed, but will change as files are added or changed.

Fifth, older operating systems did not support some of today's larger drives, so the total space reported may be much smaller than the drive specifications.

It is also worth noting that bad sectors are corrected by your operating system and can change the total drive space, free space, or used space as well.

So as long as a drive is reporting a value approximately close to the specification value, you can be comfortable that you received the right drive and that you are getting to correct data storage.  Of course, tuning of your drive's partitions and options can yield optimal values, but this is not something for the average user to explore.