I seen a video a while back where a guy took an old HDD, a 4 port USB 2.0 Hub.
Gutted the HDD, removed the outer case of the hub, took four 2gb flash drives, removed them from there case. Mounted the hub w/the four flash drives inside the HDD case, made a small notch in the end of the case so as to run the usb cable inside to the hub then put the cover back on the HDD.
You have a external 8gb back-up. When you look in my computer you will see all the flash drives with there perspective drive letter.
I'm working on one now, will let you know how it turns out.