VB6 uses the commonDialog control which is used to display dialog boxes for Colors, Fonts, Opening Files, Saving Files, Help and printer selection
You will need to add the component (ctrl+T) to your project by checking Microsoft Common Dialog 6.0 (SP3), Then you add this control object to your form. This control isnot displayed until one of its show methods is activated.
You can call these methods from any event handler (button or menu) or function.
If you want to open one of your other forms in your project then you can create a new instance of the form assigned to a variable and call a show method
Dim myFrm as New frmAbout
myFrm.show
You can use vbModal in the method to open the form modally
myFrm.Show(vbModal,Me) ' me is defined as the owner of the modal form