MAc os 10.5.2 shared tab in side panel dissapears while connected to network

The shared tab tends to do this, and this is a problem that has been reported to apple many times.
To change network settings, go to the apple icon at the top left of the screen, and select System preferences. Go to Network, and under advanced, you should be able to change things like IP address, DNS addresses, as well as NetBIOS name (computer name).
   Leopard automatically works with Windows file sharing, but you need to activate file sharing on Leopard so it works both ways. Back in Sys Preferences, go to sharing, and make you selections there. However, as I said, names aren't always show in the "shared" tab. to get around this, when you're on the main desktop, in finder, select "Go" from the top bar, and click "connect to server". In the server address, enter "smb://192.168.0.244" to access windows files systems, changing the ip address to the particular computer you want to access. This can also access any NAS that has been formatted through native windows. There are programs like MacDrive and Paragon NTFS that allow you to read the different system structures from Mac and PC. However, be careful with Macdrive, as it exposes the Mac native drive to Windows types of viruses/trojans etc. Make sure if you use it you set your windows system to scan the mac drive as well.
Hope it helps.