Windows Server 2003 Losing Shared Tab

I have installed windows server 2003 on Hp Proliant ML110 server , and my client group system is windows xp professional. shared drive missing after some interval. To get again the shared drive ,restart the server and get the shared drive.

I thought its happen due to AD , now I have removed AD and my all clients working in workgroup to map the shared drive . the same problem is also here.
plz help!!!!!!!!!!!