You are kindly asked to install both drivers - Grayscale and Colour and select as default printer the grayscale one, to avoid the involuntary abuse of colour prints.

The procedure for Windows XP is the following (the other verisons are similar):

Download and extract the zip files at the end of the document
Run the setup in Kx621113_UPD_Signed_en\Setup.exe. Select KX DRIVER and select the autodiscovered printer TASKalfa 4550ci. (If on wireless network insert the address 4550ci.iom.cnr.it)
Select "Use hostname as port name" and click Next. Based on you own preferences you can install the advanced functions and the fonts
Uncheck "Set as default printer", click on Next and click on "Install". A new window will open where you can choose the presets and the plugins. Select your preferences or cancel this step.
In the window "Installation complete" uncheck "Print a test page" and "Enable status monitoring" and click on "End"
In the printer properties click on "Automatic Configuration"; and close with "OK"

In Printers and Fax select "Add a printer", click on "Next" and unchek "Automatically Detect and Install my Plug and Play Printer" and click "Next"
Select the port 4550ci (Standard TCP/IP Port) in the dropdown menu and click "Next"
Click on "Have Disk" and select the directory where you have decompressed the KxMono.zip file
use the printer as DEFAULT and DO NOT share it
Continue even if there is a window stating that the drivers did not pass some Microsoft tests.
Wait for the procedure to complete and click on "Finish"
In the printer list click with the right mouse button on the "Mono Kyocera TASKalfa 4550ci KX" printer and select Properties and "Peripheral setup"
Check the Trays from 1 to 4 and on "Duplex unit".
In the field Memory insert 1024 and click Ok