I did a similar thing when I was a Uni, but I had only used floppies as back up so it wasn't even on the HD. I overwrote on my floppy that had three weeks work on (zipped down) lost the lot. We learn the hard way some times, lol:-))))))
These days there are so many back up options available Legolas.
If the file is too big for a floppy even when zipped, you could use smart media, compact flash or Zip disc's. CDR/W is another way of backing up as is using a tape drive.
I personally use a mixture of floppies, Zip disc's (both 100 & 250mb), back up tapes (from the server at work), compact flash and naturally the HD.
Like you have said Legolas it does come down to personal preference, and importantly I think cost what can you afford or not afford to loose?