Using NetBEUI

Our small office of 12 workstations and 3 network printers is using NetBEUI. Are main database is in Access 2000. We are having to wait long periods of time to get into the database (up to 5 Mins). We also have been getting disk or network errorsand file accessing is quite slow. My question is what can I do to improve this? Is there something I not doing? Please help.