ProE/ Creo creates versioned files every time you save a part, drawing, assembly, etc. That means if you save a part 10 times you can see 10 part versions in the folder it is saved.
To delete old versions of any part, drawing or assembly alone, just open it in the ProE/ Creo and then open the file menu from the main menu (See the picture below). You can see an option called delete. If you expand this you will see two options.