I have recently been bowled over by the power and simplicity of the e-smith Linux server from
http://www.e-smith.com/ . It installs typically in less than half an hour, works seamlessly with Windows networks offering shared files, printing, email, web serving, ftp space etc. All with an easy web-based configuration!
If you are considering moving server space to Linux, I strongly consider finding an old box and putting the e-smith software on it. You'll be impressed ...