Periodic Server/Client Maintenance Plan

I am about to contract as the network admin for a mid-sized company. The client wants periodic monthly maitenance on the (25) workstations and the (1) server–monthly on the workstations and quarterly on the server.

The server is Win2k and workstations are XPPro. The server is used strictly as a file server (no exchange, no IIS, no SQLServer, etc.) and workstations (POP3 email, virus checkers, MS Office, etc.) log in from the server.

What tasks should be performed monthly on the workstations and what tasks should be performed quarterly on the server?

Thanks.