Regarding one system or two; if your business depends on your computer, then it's always best practice to keep your business system as 'sterile' as possible, and use it only for tasks required to run your operation. Pickup a second, perhaps lower end system for general, non critical tasks. You could even use the second system as a backup to your primary business system in an emergency;
You'll thank yourself someday when you 'accidently' click on that link that ultimately takes your system out for a day or two....
like gnome said - multiple internal hard drives don't count as a good backup; at a minimum, backup to an external drive; and use a real 'backup' utility that will allow you to restore selected files, not a 'mirror' that will restore everything as is, including the files that you are trying to avoid !!!