Windows

I don't know what you consider inexpensive, but here is a link you wnat to check it out:
http://www.net3group.com/
They're among the best in the business

Good Luck!

Hi, look at www.ipswitch.com
Look at what's up 2.6 (there is also a more robust "gold" version). You'll find a listing of what the products will do and you can download a trial version so you can try before you commit. Hope this helps.

To monitor network traffic you can use NetworkMonitor from Windows NT server or better util is NetworkMonitor from Microsoft SMS. Or you can use sniffer by Network Assotiation. To identify some bottlnecks with you Windows NT you can use Perfomance monitor. To find bottleneck in Linux use command like "top", am I right? If you have SNMP enabled devices (computer with SNMP agent and printer) you can recieve warn of any computers or printers going offline and many other information but you mast buy expensive SNMP manager like Optivity. To scan you software use Microsoft SMS. I think you can not find one package, it will a set of different one. And I hope you dont need use it every time because it will decrease common performance.

Since you already have Linux experience, I would recommend MRTG
http://ee-staff.ethz.ch/~oetiker/webtools/mrtg/mrtg.html

It is a free application that will do what you have asked, and a great deal more from what I have seen.

Use Net X-RAy!!! This is really cool!
specifically: Sniffer Pro LAN or WAN

I don't know what you think is expensive but this will let you try it out and see what's up.

www.axial.co.uk