How do you share files between a pc wireless network and ibook

I recently upgraded my ibook G4 to 10.5.8 Leopard. When I had 10.3.5 in there, I was able to see all my network computers using a Linksys Router. I was able to see all files and folders that were shared on my network. Since I've upgraded, I see the ibook on my network computers but I see no files or folders. On the ibook, I see no network computers. I'm new to Apple computing so please have some tolerance and patients in explaining a solution.