I replaced a client computer on a small SBS2003 server network with another pc running windows XP Professional SP2 (same as all 4 other clients). Everything works well for a time each morning when started. I can log in, access documents on the network, print to networked printer, ping back and forth. After about 2 hours, access begins to slow down. I get an hourglass when accessing files on the server, and eventually everything hangs up. I have to restart to get back on to the server. All other clients can access everything as usual. What things can I check to figure out the problem?