Project raison expetion class EClassNotFound with message "Class TMainMenu not found"

#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
#include "Basic.h"
#include "ABOUT.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TBasicForm *BasicForm;
//---------------------------------------------------------------------------
__fastcall TBasicForm::TBasicForm(TComponent* Owner)
    : TForm(Owner)
{ Application->CreateForm(__classid(TBasicForm), &BasicForm);
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::NewForm1Click(TObject *Sender)
{
 Application->CreateForm(__classid(TForm1), &Form1);
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::Cascade1Click(TObject *Sender)
{
Cascade();
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::Next1Click(TObject *Sender)
{
Next();
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::Previous1Click(TObject *Sender)
{
Previous();
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::Minimize1Click(TObject *Sender)
{
for(int i = MDIChildCount-1; i >= 0; i--)
   MDIChildren[i]->WindowState=wsMinimized;
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::Closeactive1Click(TObject *Sender)
{
  ActiveMDIChild->Close();    
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::Closeall1Click(TObject *Sender)
{
for(int i = MDIChildCount-1; i >= 0; i--)
    MDIChildren[i]->Close();    
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::Exit1Click(TObject *Sender)
{
Close();    
}
//---------------------------------------------------------------------------
 
void __fastcall TBasicForm::N1Click(TObject *Sender)
{
AboutBox->ShowModal() ;
}
//---------------------------------------------------------------------------
 
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