error al conectar programa al sql

intento conectar un programa con una bvase de datos en sql pero me aparece
este error, cosa que no aparecia hasta que creé una nueva instancia en
ODBC
para conectar el cristal reports a la base

este es el mensaje que me arroja:

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.Data.SqlClient.SqlException: SQL Server does not exist or access
denied.
at System.Data.SqlClient.SqlInternalConnection.OpenAndLogin()
at System.Data.SqlClient.SqlInternalConnection..ctor(SqlConnection
connection, SqlConnectionString connectionOptions)
at System.Data.SqlClient.SqlConnection.Open()
at EMPRES.Mod_Gbl.SQLDB_Open(SqlConnection& SQL_CON, String str_db) in
C:\EMPRES\EMPRES\Mod_Gbl.vb:line 17
at EMPRES.Login.cmd_Ingresar_Click(Object sender, EventArgs e) in
C:\EMPRES\EMPRES\Login.vb:line 192
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.PerformClick()
at System.Windows.Forms.Form.ProcessDialogKey(Keys keyData)
at System.Windows.Forms.Control.ProcessDialogKey(Keys keyData)
at System.Windows.Forms.Control.PreProcessMessage(Message& msg)
at
System.Windows.Forms.ThreadContext.System.Windows.Forms.UnsafeNativeMethods+IMsoComponent.FPreTranslateMessage(MSG&
msg)


************** Loaded Assemblies **************
mscorlib
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.2032
CodeBase:
file:///c:/windows/microsoft.net/framework/v1.1.4322/mscorlib.dll
-
EMPRES
Assembly Version: 1.0.2118.32514
Win32 Version: 1.0.2118.32514
CodeBase: file:///C:/Sistema/EMPRES.exe
-
System.Windows.Forms
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.2032
CodeBase:
file:///c:/windows/assembly/gac/system.windows.forms/1.0.5000.0__b77a5c561934e089/system.windows.forms.dll
-
System
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.2032
CodeBase:
file:///c:/windows/assembly/gac/system/1.0.5000.0__b77a5c561934e089/system.dll
-
System.Drawing
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.2032
CodeBase:
file:///c:/windows/assembly/gac/system.drawing/1.0.5000.0__b03f5f7f11d50a3a/system.drawing.dll
-
System.Data
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.2032
CodeBase:
file:///c:/windows/assembly/gac/system.data/1.0.5000.0__b77a5c561934e089/system.data.dll
-
Microsoft.VisualBasic
Assembly Version: 7.0.5000.0
Win32 Version: 7.10.6001.4
CodeBase:
file:///c:/windows/assembly/gac/microsoft.visualbasic/7.0.5000.0__b03f5f7f11d50a3a/microsoft.visualbasic.dll
-
System.Xml
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.2032
CodeBase:
file:///c:/windows/assembly/gac/system.xml/1.0.5000.0__b77a5c561934e089/system.xml.dll
-

************** JIT Debugging **************
To enable just in time (JIT) debugging, the config file for this
application or machine (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

<configuration>
<system.windows.forms jitDebugging="true" />
</configuration>

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the machine
rather than being handled by this dialog.