At the moment, I have lost my operating system on my laptop about 6 times this year, primarily due to data corruption. After several lessons in doing proper backups I’ve finally found a method that works instantly and can be left alone after it’s set up. I’m using Dropbox, a free tool for keeping a directory synced with a server. It couldn’t be used as the only part of the setup as it can’t sync any chosen directory, only its own. However, I’m using PureSync (also free) to keep multiple directories synced to the Dropbox directory. When a file is updated PureSync sees the modification and copies it to the Dropbox directory, where it gets stored online. In theory, you could have multiple computers using the same Dropbox, which would maintain current copies of your Documents/Photos/etc. folders across all computers.