How the did you get 12.04? And I doubt many people can help you. But in anycase try to install Samba.
For installation of Samba, Open terminal window (Alt+F2 and type: gnome-terminal) and copy the following commands in the Terminal:
sudo apt-get install samba samba-common system-config-samba
When installation finished, Now you need to that folder which you want to share or you can make a new folder.
sudo apt-get install samba
Note: Then go to Software Center and Search "glade" & "python-glade" and install both of them
Now start the Samba Server Configuration press(Alt+F2 and type gksu system-config-samba). To add a folder which you want to share click on the + button followed by click on the browse button. Now select the folder which want to share on network. Now enter description and check your folder writable or visible settings. Click on the access tab and give access to the user you want, when you finished click on the OK button. Now your folder is added to your Samba Server Configuration.
Now go to the shared folder, Select the folder then right click on the folder and select Sharing Option. Here add a comment and change the permissions for others to create/delete/modification in files/folders and for the guest access rules.
Samba is Sharing service between Ubuntu to other networks (Windows, linux and others).