Supplying user credentials to Sharepoint 2 from a client program

// C#
myCredentials = new System.Net.NetworkCredential(username, password, domain);
mywebs = new SPWebs.Webs();
mywebs.Credentials = myCredentials;
mylists = new SPLists.Lists();
mylists.Credentials = myCredentials;

Re-install the Server Service

To re-install "Server Service" in Windows 2003/XP, delete and re-install "File and Printer Sharing for Microsoft Networks" in network connection properties of your current network connection. Reboot in between.

Re-installing the Workstation Service

To re-install "Workstation Service" in Windows 2003/XP, delete and re-install "Client for Microsoft Networks" in network connection properties of your current network connection. Don't forget to reboot in between.