how to detect NT network slowdown causes

We have an all-NT network — 1 Dell server (running Msoft Small Business Server 4.5), and 16 NT workstations, (128 MB RAM, running Office 97 and some DB app’s). we have a new Intel 24 port 10/100 switch, and all the connections are 100 MBIT.

So…how do i discover why workstation performance slows down–sometimes? Outlook (2000) will just hang there for awhile, and come back in a minute or so, just as an example. another example–logging on can be very slow.

what tools can i use to see what’s going on?

thanks!

fred