You have 300GB hard drive in your computer,but the most of very important data you have that drive will lesser.if a folder of your photo and gallary,songs,pictures,videos and then important files or documents.

The take complete the backup of the drive any time is consuming process,are you can use Microsoft SyncToy for selectively in a backup and than certain folder between in the hard drive and external USB drive.you have do is plug in the drive in a backup the folder.