DPC Latency Checker examines your PC to make sure it's able to play real-time audio or video streams properly, without interruptions or dropouts. And if there's a problem then you may be able to use the program to track down the precise cause.

Getting started is as easy as launching the tiny (294KB) portable executable, and watching for a few seconds. The program will begin checking the time your system is spending in processing Deferred Procedure Calls, a mechanism used by drivers to request urgent attention from the CPU, and graphing the results.

If all is well then the graph will stay resolutely green. Which means that any dropouts you're having aren't related to DPCs, and the program won't be able to help.

If you regularly see one or more red bars in the graph, though, this means at least some of your DPCs are taking an excessive length of time. In other words, one or more drivers on your PC are taking up so much time doing their own work, that you just don't have the system resources left to handle streaming audio or video without dropouts or interruptions.

What next? The simplest approach is probably to try disabling various non-essential devices in Device Manager, while DPC Latency Checker continues to run in the background (the author's web page explains more, including some important safety concerns - be sure to read it). If the red bars disappear after you've disabled a particular device then you have the culprit: check for a driver update to try and resolve the problem.