Very Slow Logon Speed

Our LAN became very slow recently. All lan users have to wait for at lease 15-30 minutes to logon to our domain built on W2K server.

This was not that case in the past. We could logon to the domain immediately.

I have checked any virus infection by using the online scan services provided by different compaies but the results are all negative.

So, I wonder what’s wrong with our LAN. Anyone has any idea?