Ok, so I installed Ubuntu 8.04(guest) into Ubuntu 10.04(host) and everything is running fine. I have been trying to share my /home folder to open it while using Ubuntu 8.04 (guest). I am using Virtualbox, Guest Addittions and both operating systems are updated. I also added my user to vboxusers group and it does not work. I was able to share files when I had Ubuntu 12.04 as host but now I do not know why this do not work with my Ubuntu 10.04. I had opened "/home" that was located in "media" but now it does not work with 10.04 host and 8.04 guest. That's all. Thanks.