Network bandwidth monitoring

I am not sure if such a tool exists as neither does anyone else I know, but.. does anyone know of any software I can install on a system to see what machine is sucking out all of the internet bandwidth? I am admin of a Windows domain with about 15 - 20 users at any given time and too often it is slow because someone is uploading/downloading something and tracking it down is difficult. Unfortunately the networking hardware is all mostly residential class (the setup predates me, not taking the blame there). My domain controller handles all DHCP and DNS. Anyone know of anything I can add to it to see some real-time statistics?

 

i remember nick s showed me port reporter years a go. i don't know if it's what you need though i can't really remember exactly what it did now, your post just made me think of it. it may help.
http://support.microsoft.com/kb/837243

 

Jack,

Have you ever tried out Spiceworks? I cant remember if if has bandwidth monitoring but it does a lot and its free.

http://www.spiceworks.com/

PRTG Monitor is nice. I use it here at my work, but its not free.

 

Thanks, I'll check that out regardless as it looks like I could make use of it.

 

@Trooper
thank you for bringing this amazing software to my attention

 

Jack, let me know how you like it.

@treehouse786

You are welcome. Its a really nice product!