How can i reduce these GDI and User objects in .NET MDI form

Question

Dear all,
I am working on .Net3.5 windows application.The project is for call center people.While calls are coming and attempting to give some data, the GDI objects and user objects are continuously increasing.After i made 100 calls the GDI and User objects range will be greater than 4000 so at that time application is not working.

So how can i reduce these GDI and User objects in MDI form