Open a command prompt by going to Start-->All Programs-->Accessories-->Command Prompt.

Type in the following EXACTLY AS WRITTEN making sure to maintain upper/lower case:

SQLCMD -S LOCALHOST\HORTPROSQL

You should get a response of the following:

1>

If you don’t get this response,  the message displayed may provide some diagniostic information to help you establish a connection to the SQL Server. If the SQLCMD cannot communicate with the SQL Server, then HORTICOPIA Professional will not be able to communicate with it either. Also, if HORTPROSQL is running, it’s most likely that this is an account privileges problem. 

Other possibilities are that the SQL Server 2005 Express was not installed properly.  On a client computer, it’s also quite likely that there are firewalls on the Server preventing client access.  Please consult your Networking User Guide.