At one point in time, Windows came with the optional Network Monitor component. While it had its quirks and had a bit of a learning curve, it was useful, free, and ubiquitous whenever I needed to perform network traffic captures. (Mind you, this was back in the days when we were still using hubs, not switches, and could listen to everyone's traffic over the wire.) Then came the dumbing down of NetMon; it wasn't included in XP, and if you were using it on a server you could only sniff traffic originating from or destined to that server, unless you had SMS and could use the "full" version of NetMon. If I was just doing a quick one-off investigation, this wasn't bad; if I was trying to monitor a set of related interactions on multiple machines, this restriction became unliveable.
Well, MS has finally released Network Monitor 3.0 as a free download, and they've removed the restrictions. It includes support for 64-bit platforms. I haven't downloaded it yet, but it's in my little list...