If you are on a network, you can try the net send command.
Simply open a command prompt and type: net send <username> <message>
The username is the user's name on the network whom you try to contact.
My Computer
At a glance
Windows® 8 Pro (64-bit)Intel® Core™ i5 Processor 2467M (1.60GHz, 3MB...6GB DDR3 System Memory at 1,333MHz (on BD 4GB...AMD Radeon™ HD7550M 1GB DDR3 (Ext. Graphic)