I had the same problem when I was recording at 576, try manualy changing the resolution on the EasyCap by cutting it in half i.e, 576 to 288 or 480 to 240, keep the resolution in your capture software to full though, either 576 or 480. That should pretty much half the amount of CPU load.
You can check your CPU load by right clicking the task bar and clicking on Task Manager, do this while trying to capture and it will give you an instant realtime CPU usage readout of which programs are using processor and RAM resources at any given instance.
If you want to capture at full quality with very low CPU load then try a different video capture program like AMCap, click
here to get a realy good modified version. This is just a demo and will only capture for 20 mins before timing out and asking you to buy it! Click
here for AMCap FAQ's.