Help!My computer has crashed 3 times in the past 6 mo. due to various reasons (probably my inexperience) Every time this happens, I loose my pictures, sent e-mail and Microsoft updates. What product should I purchase for a back up if this happens in the future?

The Seagate backup external hard drive in your last sales flyer looks like it might be the solution, but I am not sure what size to buy. Could you advise please?