slow logon

I am running a network that consists of A windows 2000 server and windows 2000 pro clients. for some reason when i came back from the holidays it was taking a very long time to log into the network. it takes almost 10 minutes to bring up the logon screen and another few minutes to get the desktop up after you enter your name and password. i have tried rebooting the server but it did not work. i have no idea what to do. thank you in advance