Logon failure: the user has not been granted the requested logon type at this computer

If you see this message the following should be done on the computer containing the shared files:  

Download the following and install it

Windows Server 2003 Resource Kit Tools

http://go.microsoft.com/fwlink/?LinkId=4544

after installation is complete, click on: Start, All Programs, Windows Resource Kit Tools, Command Shell

Then enter the following commands. (Attention: they are case sensitive.)

net user guest /active:yes
ntrights +r SeNetworkLogonRight -u Guest
ntrights -r SeDenyNetworkLogonRight -u Guest
 

The first command enables network access for Guest, the two subsequent ones change two different policies to allow network access for Guest.