You say you are trying to connect over TCP/IP, however using the server windowsserver/SQLEXPRESS
will use the default Named Pipe transport. You have two options:
Really use TCP/IP. Specify the server in the form of
\\windowsserver\SQLEXPRESS
which should tell the driver to use the Network Transport.Enable the Named Pipe transport. You can do this by going to Start->Programs->MS SQL Server 2008->Configuration Tools->SQL Server Configuration Manager. Then under the SQL Native Client Configuration option make sure the Named Pipes is enabled.