Problem with Reference to assembly

[@myg@l]

Error 1 Reference required to assembly 'System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=969db8053d3322ac, Retargetable=Yes' containing the type 'System.Net.Sockets.Socket'. Add one to your project. C:\Documents and Settings\@myg@l\My Documents\Visual Studio 2005\Projects\Merchant\Merchant\Form2.vb 11 21 Merchant

Wat does this mean?

regards
amygal