Long horn is the new version of Windows currently being worked on by Microsoft. I'm not sure when it's due for competion or release. It has nothing to do with Linux, butalot of features that Longhorn has, were, in some peoples eye's, 'stolen' from Linux. I'm not a Linux guy, so I cant explain to you what they are, but I do know they exist. Nothing to do with Linux, but alot of times compared to Linux and the such.
