Heck- you wouldnt even need a hard drive on a separate computer or server. You can add a secondary hard drive on the existing computer for your images at a lot less cost or a lot more storage. If you dedicate that drive for your photos, the chances of viruses to damage the files would be minimal unless you saved an image that contained a virus. Also for backups, usually 2 on a different media (CD, DVD, Zip) are typically enough. The main thing to remember is to keep them at different locations. These media could always be copied if one (the other) was damaged.