I assume you're talking about the model file history, and not any WIndchill based history of actions.
There is no menu pick or configuration option to delete the file history of which I am aware. However, if you just need the features/geometry, you can copy all the features from the original model, create a new empty model (not using a start model because they will have a history too), create at least the default CSO in the new model (default datum planes help as well), and then paste the features into the new empty model. You'll lose some data using this method (relations, parameters, layers, etc.), but you can bring some of that data over as well using other methods.
Regards,
Dan N.
