i don't see how anyone can say they don't believe in ghosts. if you haven't seen one, then you haven't seen one. you don't know if they exist or not. if you've seen one, you believe.
i saw one when i was about 19. it was an old lady and she appeared in front of me in my grandmother's house. i had always felt that place was haunted.
here's a long weird story:
a relative of mine says that when she was a little girl, she used to get up in the middle of the night once in a while to use the bathroom, and every few months, she would encounter a family of chimps, eating breakfast, in the kitchen. she remembers very vividly a mother and two children, all dressed in human clothes. she would walk past them on her way to the bathroom and they would continue with their breakfast without paying much attention to her. so, for years and years she never told anyone about this, because she assumed no one would believe her.
recently, as an adult (she's in her 50s), while conversing with her sisters, she decided to spill the beans and tell them the story of the chimps she had seen as a child. it turns out her sisters saw the same thing, and they too never told anyone for fear of being called a liar, or crazy. they discussed what the chimps wore, what they ate, everything was the same. they had seen the exact same thing.
when i was told of this i figured there had actually been a family of chimps, dressed as humans, eating breakfast in the middle of the night at her house, but everyone believes they were ghosts.