windows is the the best for desktop, gaming and easiest to use for a no IT professional, the kernel of it is designed by David A. Solomon, one the the greatest coder in the world. in pc server field freebsd or openbsd is better than Linux on stability and efficiency. Mac OS X's kernel is Darwin which is similar with freebsd, why not use the kernel of linux, there are always some reasons. tcp/ip is original from BSD unix. most of the kernels above are Monolithic kernels, which have been existed for more than 30 years, tested and efficient. for my personal point of view, I prefer micro-kernel based os, such as QNX and Vxworks. anyway Linux is growing quickly now for the investment of huge companies like IBM, and Linux is the best os to build cheap and powerful cluster. as far as I know the name of the state of the process is changed in Linux kernel 2.6.