Licensee has become a major threat with the companies which cant afford for original OS due to Cost. Linux is a solution for all these threats. Since Linux is GPL(General Public License) and free OS, it can be installed on any number of systems. Linux has the best desktop, the look and feel are really touching and there are good applications which can match your existing windows OS. Rest requires a customization according to your needs. Some of the applications which can be used are:

Desktops Gnome,KDE,XFce4
Mail Clients Evolution(clone of Outlook Express),Kmail,Mozilla Mail(ThunderBird)
Office Suite Open Office(like MS Office)
Graphics GIMP(like Phtoshop)
Browser Firefox, Mozilla, Konqueror
Audio XMMS (like Winamp)
Video Xine,Mplayer
Games Good Games