The difference Linux server and windows server

The different between windows server and linux serve

With Linux, the operating system is effectively free

Windows, there are licensing fees for any version, so there is a cost factor

With linux, you have to make modification kernel

Windows, it's a stable platform, though not as flexible

This answer is pick up from Phil Cox, principal consultant with System Experts interview

And from the other resource

Server that based on Linux, for example, qmail that equal to MS exchange server, can work at a Pentium 1 computer with only using RAM 64MB or less. Linux has a TUI (text user interface) for administrating the system, fot example, YaST in SUSE and drakxconf in mandriva, that can run without X Window.

As a OS server, linux is design not to often for shutdown in the operation, defending from the memory leak in linux have more concern than windows