If at all possible what I do is run all my most important information off "what most would call" a junk computer. Basically something that can stand running windows XP/server 2003 and secure store all my information off my main computer. What typically happens, by no bad intentions at all, a website is gone to (or email) that contains simple spyware. These can affect any file on your computer, even your returns, and software itself. Usually if someone is well protected from these types of issues they have little to no concern. There is times, not all the time but there is times, that a virus scanner/spyware remover accidently corrupts a file while trying to get rid of it. This can cause the beginning process of a virus to take place but not fully. Which this can lead to your system crashing out completely. There is a reason why people do pay the extra $ for a top company such as Norton, McAfee. I have heard even some good reviews on AVG, but I don't personally like their firewall system. These accidents can be googled or searched on yahoo.
With that, the best thing to do is network most of your important information through a secure username/group. That way there is 1 entry point for data. For instance, if you have a junk computer/server running you would just set an administrator password that only you know. Once thats done, you would then make your main computer (host, main admin computer) and have this computer pull the information from the secure'd computer through 1 point. You would also want to organize all your folder data inside a main folder. This way you won't have to try to copy your WHOLE hard-drive, just your important things. You then can do daily backup/overwrites each night when you leave onto an external hard-drive or good USB Flash drive. I would recommend the Flash Drive since they have ones that stay on your key chain that hold up around 50gb.
This can be seen as "over the top", but this is a really guaranteed backup efficiency system you can do between 2 computers and an external.
You are also open to online backup storage. There are a few good ones out there, but no matter what decision you decide to go with its always best to have your data on a secure/non-active computer.