Linux
I have been using linux for 15 years now. When I started, there was no x-windows. Only console. And installing linux was very hard. But after you installed it once or
twice it became very easy. If you use linux you have much less worry about all the trojans and such going around, Mainly because there is not as many users running linux. I still run windows on two of my boxes. I started out running redhat, then went to Mandriva (formally Mandrake) for a number of years. Then switched to SuSE. I am now currently using PCLinuxOS. I highly recommend this distro, for the ease of installation and use. They have done a fantasic job on this distro. I have also tried others through the years. Such as ASP, Caldera, Corel, Gentoo, Linspire, Sprio, Turbo, United, Ubuntu, Kubuntu and Xandros. I have also tried BeOS and QNX. But there wasn't many applications for it.
Few Linux Flavors