Windows 2003 - How to tell who is using the most disk time

Start off with perfmon and determine the bottleneck.
Is it network, memory, cpu or disk I/o's
What is slow?  a file share? database etc?
To my knowledge the only way is to buy an expensive sniffer that will analize all the IP traffic.
A free version but much harder to use exists called etherreal which was renamed to wireshark.
http://www.wireshark.org/
 
it is not near as easy to use as something like network observer.. but uses the same techinques.

I mentioned it 2nd because there is a good chance its not your network maxing out.
 

ecszone, I only notice that the slowness occurs when someone is either writing or reading a large file to the file server.
I wish there was a something that would show something similar to the Shared Folders -> Sessions view but maybe have a bandwidth monitor by user. It would be nice to know who is taxing the server at any particular time.
I believe the CPU, memory, hard drive, & network is okay, only when someone transfers a large file. I am trying to pinpoint who is doing this. I am familiar with etherreal and do not have that kind of time to go through each packet.

YOU CAN USE  PACHETAGE SNIFFING PROGRAMS  OR EVEN  NETWORK MONITOR PROGRAM
TO VIEW ALL TRAFFIC OCCOURS AT YOUR NETWORK
YOU CNA FILTER THE NETWORK MONITOR TO CERTIN COMPUTER AS YOUR SERVER
KIND REGARDS
MOHAMED ZAIED
MCSE + SECURITY

mtzmind, you are correct! I was wondering if there was an easy way to do this. I was hoping there would be a perfmon counter that I could check instead of packet sniffing.
Would anyone be able to recommend a GUI type bandwidth monitor that specifically shows who is connecting and how much bandwidth they are using?

NETWORK MONITOR CAN DO THIS  
TRY IT
IT CAN BE USED AS ALARM TOO