All hard drives require formatting before you can use them on your computer. Some external drives -- such as those that come with backup software pre-installed -- come formatted out of the box, but other times you'll need to format the drive yourself. Drives that have never been formatted won't appear in the Windows 7 "Computer" window alongside your system drive, so you need to use the Disk Management utility to set up your drive.
Connect the external drive to any open USB port on your computer. If the drive includes a power adapter -- some run off of power from the USB port -- plug it in and turn the drive on.
Wait while Windows automatically installs the driver for your hard drive. Windows 7 will display a notice in the taskbar stating "Installing device driver software," and will let you know when it finishes.
Open the Start menu, right-click "Computer" and click "Manage." If you're not using a Windows administrator account, the system will prompt you for an administrator's password to continue.
Click "Disk Management" in the Storage section of the left panel. A graphic representation of your drives and their partitions will appear in the bottom part of the window.
Right-click on the "Unallocated" bar, which represents your new drive, and pick "New Simple Volume." If you don't see an unallocated section, and instead all partitions display "Healthy," your drive is already formatted.
Click "Next." Leave the volume size set to the drive's maximum unless you want to make multiple partitions and click "Next" again.
Pick a drive letter for the new disk from the drop-down menu. This letter applies only to the computer you're currently using -- if you plug your external drive into another computer, it may use a different drive letter. Press "Next."
Leave the formatting settings on their default options, unless you plan to also use your external drive with a non-Windows computer or one running a pre-XP Windows system, in which case you should change the file system to "FAT32." If you want to name your drive, enter a volume label in the text box.
Click "Next" and then "Format" to finish.
Optionally, you can uncheck "Perform a quick format" in the formatting options. The primary benefit to a full format on a new drive is the inclusion of a bad sector check, which can let you know if your new disk has a hardware defect, but full formats take significantly longer.
Connecting your drive via eSATA, if supported, will significantly speed up a full format compared to USB 2.0. If both your drive and your PC use USB 3.0, however, there's no need to switch to eSATA.
Formatting will permanently erase all data on a drive.
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