LagMeter

Here it is, a powerful software application that finally gives you the ability to not only measure the Lag you live with in your games, but also to understand where your lag-related problems are coming from. Finally, the causes of your Lag will not be a mystery because LagMeter will tell you if it is your gaming PC, the network, or the gaming server that is giving you grief. Version 0.2 build 2334 may include unspecified updates, enhancements, or bug fixes.

Requirements:

Windows XP, .NET 1.1