Hi Anas,

Here some Unity 4.2 guides to get you started;

Cisco Unity 4.2 System Requirements

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/prod_system_requirements_hardware09186a008061eb2a.html

Supported Hardware and Software, and Support Policies for Cisco Unity 4.2 and Later

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/prod_system_requirements_hardware09186a00806cd9d2.html

Cisco Unity Documentation Addendum, Release 4.2

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_administration_guide_book09186a00805eb63a.html

Cisco Unity Documentation Guide

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_documentation_roadmap09186a00801179df.html

If you have more questions don't hesitate to ask, there are some great people here like Tommer, Ginger, Jeff and many others who have been of great help to me :)

Take care,

Rob