There's a little trick that the Windows operating system uses to allow high-priority tasks such as video and audio drivers uninterrupted access to the CPU - the Delayed Procedure Call. A DPC puts off the inevitable until the system feels there's time. Unfortunately, DPCs only work to a point and can't always avoid disturbing high-bit rate audio and video recording, which requires an uninterrupted data flow.
If interrupted for too long, as with a long-delayed DPC, you will hear dropouts and static. DPC Latency Checker (free) displays the amount of time these DPCs are taking so you can tune your system by disabling tasks or hardware that cause DPC spikes. See all: PC Advisor software downloads
A display of your computer's latency (how long it takes before tasks are processed) is all there is to DPC Latency Checker--use it to tune your system for audio and video. Open up DPC Latency Checker and you'll see a real-time display of the latency of your system. If there's something generating CPU-hogging DPCs, it'll show up as spikes on the left-scrolling graph. It's much like the Performance tab found in Windows Task Manager, except it's for DPCs.
Simply keep an eye on DPC Latency Checker's graph while you disable and enable various hardware and background applications using and when the spikes disappear, you know you've found the culprit. The Wi-Fi and battery monitors on laptops are notorious for generating fat DPCs, so that might be a good place to start your hunt.
Even on a fast Intel Core i7 or Phenom system, you'll find that you can record higher bit rates and use more real time FX after you've disabled fat, DPC generating apps and hardware.