|I recommend that you install a virtual machine. Either VirtualBox or MS VirtualPC to start.|
Then you have a windows application that is really a software computer. Your vista install is fairly safe.
Then consider what you mean. True Unix is a very few distro's. One such is Solaris and OpenSolaris I suggest you at least try the OpenSolaris Live CD.
What you may mean is Linux, or BSD. See distrowatch.com for ideas.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10