One Megabyte?!! What the?
Hmm... I'm just thinking... I mean in a way, there must be a way of doing it. Maybe a program that will convert the file to a lower bitrate and somehow convert it back again...
If I were you, I'd probably buy an external Hard drive and backing them up on there, but then you have the problem, that its a hard drive and can still go. But you do have the added support that its very very unlikely both will go at the same time, especially if the External isn't connected all the time.
Another way to make it faster would be to use a program like Norton Ghost which could compress the files for you, and restarts in Dos and you simply keep swapping DVD's or whatever until everythings copied, so you don't have to copy files seperatly until you run out of space, etc.