Not able to open NMSP designer client: " Could not load file or assembly 'Microsoft.SharePoint" (4257733)

Notes Migrator for SharePoint will not open and it throws an exception:

System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' or one of its dependencies. The system cannot find the file specified.
File name: 'Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c'
at Quest.NSP.SharePoint.SharePointDirectAccess.CanBrowseWebApplications(Boolean administrationWebApplications)
at Quest.NSP.Migrator.SharePointCommon.IsSharePointBrowsingEnabled(Boolean administrationWebApplications)
at Quest.NSP.Migrator.JobDesignerControl.v()
at Quest.NSP.Migrator.JobDesignerControl.a(Object A_0)
at Quest.NSP.Migrator.Options.OptionsSavedHandler.Invoke(Object sender)
at Quest.NSP.Migrator.Options.Save()
at Quest.NSP.Migrator.MainForm.a(Object A_0, FormClosingEventArgs A_1)
at System.Windows.Forms.Form.OnFormClosing(FormClosingEventArgs e)
at System.Windows.Forms.Form.WmClose(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at Quest.NSP.Migrator.MainForm.a(Message& A_0)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)