don't expect to have a valid answer to this question, and I'm not talking just here on Yahoo!Answers.
You may go to a psychic and they may either con you out of your money, or the same powers that be that are causing these unexplained occurrences will be providing the answer...which will just lead to more questions.
When it comes to stuff like this, all I can say is it is designed to make you ask questions and wonder what is going on. Whatever spirits, entities, powers, phenomenon, or whatever these are, you can be sure of one thing: you will never have an answer...
...and that is why they do it. These occurences are all smoke and mirrors. They are used to trick people into believing in certain things, they are designed to make people believe that these things wield a certain amount of power. They are made to make people feel certain feelings and emotions such as fear, sadness, anger, and other feelings...usually negative.
These "entities" are always of a negative nature...even if they fool people into thinking they are of a positive force at first in order to get people to "accept" them. If they did indeed have the power that they deceive people into thinking they have would certainly do much more than just turn on your desktop.
It probably takes a very great amount of effort on their part to pull off the "occurrances" that they do.
Just remember this: no matter what happens, keep whatever strength and goodness you have within your heart. Because this is ultimately what they are out to change within you. If they can intrigue you, create fear within you, and manipulate your feelings, emotions, and beliefs, they can ultimately have the potential to ruin any good you have within your heart and replace it with negativity. Do NOT try to communicate with these things!!
(don't ask me how I know this)
Yes, people won't believe you when you tell this story. That's understandable. Do you know why some people believe in stuff like this while others don't? Because there is really only one way to realize that occurrances such as this happens: to experience it firsthand.
Show me someone that doesn't believe in something like this and I'll show you someone that has never experienced an unexplained occurrance.
Once they do, though...
once it happens to them...