Weird Problems, same machine but multiwindows

[timothyboyboy]

Hi everyone,
I am a new user for virtualbox.

I had installed Ubuntu on it. Running on windows 8 hp machine.
After I installed those guest additional stuff.
When I turn on the machine. There're 3 same Ubuntu machine appear at the same time.

They are the same, when I type a word in one of them, it appears on three of them.
When I tried to turn one of them off, all of them will off.

What happened?

[noteirak]

You've setup multi screen in the VM config, set it back to 1.