This is a simple hack.
If you want emacs to backup the files you edit just put this line on your .emacs file:
(setq home-backup “MyDir”)
just replace MyDir with the directory you wish to save your backup files to.
If you are like me you want to carry your emacs with you everywhere in your USB hard drive. PigPog has the solution here.
Using that hack you can use the following line to back up directly to your USB hard drive:
(setq home-backup (concat (getenv “HOME”) “Backup/”))
The above line backups the file to your %HOME%/Backup/