Disable CRM Form

All MS CRM Controls have a common Disabled Property.
In order to disable the entire form you need to disable each and every control.

function OnCrmPageLoad() 
{ 
  ToggleFormFields(true); 
} 

function ToggleFormFields( disable ) 
{ 
  for( var i = 0 ; i < crmForm.all.length ; i++ ) 
  { 
      if( crmForm.all[ i ].req ) 
          crmForm.all[ i ].Disabled = disable; 
  } 
} 

OnCrmPageLoad();