Install reputable antivirus software
First of all, you need to install a reputable antivirus. There are plenty of programs available on the web. In order to get more secured one, buy a CD and register yourself with the manufacturer. Update it and get the latest version. Norton Antivirus and Nod32 are the most used programs in this category.
Connect External Hard Drive
After getting a reputable program, connect your external Hard Drive through USB or any other port. The new Hard Drives support USB connection.
Wait for the system to recognise your hard drive. The system will automatically come up with a message, saying that a new drive has been found.
Run Virus Scan
Open your antivirus program, and run a complete scan. It may take plenty of time. To save time, you can make this procedure more specific.
Open ‘My Computer’, where you will find the icon of the recently-attached hard drive. Right-click on the drive, select the option that says ‘Scan Hard Drive’. The latest versions do offer this option; however, if you don’t find it, run scan for your entire machine, which is time consuming though.
Open Hard Drive after scanning
Don’t ever open the external Hard Drive before scanning, because the virus will automatically creep into the other hard drives. Once the scanning is done, you are free to use your external hard drives.