电信机顶盒播放u盘:有关vb与access数据库的连接问题

本人刚学vb，有些初级问题需要大家帮帮忙！
我在设计学生管理系统时，在工程中建了个模块，代码是：
Option Explicit
Public connstring$, UserName$, UserID$
Sub main()
connstring = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & App.Path & "/CourseMis.mdb"
frmLogin.Show vbModal
If frmLogin.LoginSucceeded Then
frmMain.Show
Unload frmLogin
Else
MsgBox "无权登录本系统", "登录"
End
End If
End Sub
还有个登录界面：
Public LoginSucceeded As Boolean

Public Sub Form_load()
LoginSucceeded = False
End Sub

Private Sub cmdCancel_Click()
End
End Sub

Private Sub cmdOk_Click()
Dim Conn As ADODB.Connection
Dim rs As ADODB.Recordset
Dim strUserID$, strPassword$, strSQL$
Static Count As Byte
strUserID = Replace(Trim(txtUserName.Text), "", "")
strPassword = Replace(Trim(txtPassword.Text), "", "")
If strUserID = "" Then
MsgBox "用户名不能为空，请输入用户名！", , "登录错误"
txtUserName.SetFocus
Exit Sub
ElseIf strPassword = "" Then
MsgBox "密码不能为空，请输入密码！", , "登录错误"
txtPassword.SetFocus
Exit Sub
End If
Set Conn = New ADODB.Connection
Set rs = New ADODB.Recordset
strSQL = "select * from users where userId="" & struserid & """
strSQL = strSQL & "and password="" & strpassword &"";"

Conn.Open connstring

rs.Open strSQL, Conn
If rs.EOF Then
Count = Count + 1
MsgBox "用户名不存在或密码错误！", , "登录失败"
txtUserName.Text = ""
txtPassword.Text = ""
txtUserName.SetFocus
Else
LoginSucceeded = True
UserID = strUsersID
UserName = rs("UserName").Value
Me.Hide
End If
rs.Close
Conn.Close
Set rs = Nothing
Set Conn = Nothing
If Count >= 3 Then
MsgBox "超过登录次数，无权登录本系统！", , "登录失败"
End
End If
End Sub
但运行后老说[microsoft][ODBC 驱动程序管理器]未发现数据源名称并且未指定默认驱动程序。
我明明在模块的代码中有定义连接数据库CourseMis,
connstring = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & App.Path & "/CourseMis.mdb"
这是为什么？快帮帮我！急用！