I don’t like the iTunes software that much - it is slow and big and the only reason for me to use it is that it is the offical software that comes with the iPod. I recently ran into a problem which was fixed pretty fast by a quick tip that I found at one tip a day. I assume that iTunes is already installed at least on your main computer and you want to access the same library of songs that are stored on the main computer.
You need to locate the file iTunes Library.itl on this computer which is usually stored in username\My Documents\My Music\iTunes. You need to share the folder iTunes. To do this right-click the iTunes folder and select Sharing and Security from the context menu. If there is no Sharing and Security entry you will have to enable simple file sharing by clicking on Tools and selecting Folder Options.