Brother Caedmon was as an illeterate peasant and then by the miraculous intervention of God (or dare I suggest some manipulative Abbess or Abbot of Whitby? :-) ) suddenly found he could write beautiful poetry and prose.

Anyway, back to the plot. Use standard backups by all means - they are fine to keep your important files. What happens if your PC blows up though? What happens if all the PCs you have suffer the same virus?

If it is that important just buy another PC of the same or better spec. Load it in exactly the same same way. Keep it off your netwrok, preferably at another office, and update the data every time you feel that you would loose too much if everything went down! At less than £300 for a good working PC it isn't exactly out of the question! You could even dual boot it and use a second disk for trialing updates to the software or OS.

Cheers

DtG