Looking through different operating systems, I found those that had been based on Berkeley Software Distribution (a.k.a. BSD) and one of them I found very nice for me.It is PC-BSD. I watched the video on Spatry's channel So, I decided to try it, but before downloading, I caught its size, it's about 3.6GB. So, I found another one that also fits me, it's Xubuntu, http://www.linux.org/threads/x-ubuntu-installation-over-slackware.6067/ it's size is 913MB. I also checked Windows 7 Ultimate, it is also about 3-4GB. So, why Linux operating systems are pretty lightweight, while the others are so huge? Thank you!