I believe I have been having this problem ever since I installed McAfee, i dont want to reinstall it. Well anyways every 2-3mins, my pc laggs for 2-3secs, the mouse goes slow and the sound jutters. It happens anywhere regardless if I play games or idle on the desktop.
Try closing out other items in your taskbar that don't need to be running (weatherbug, HP print software, quicktime etc.). Those programs use up a lot of RAM at no benefit to you unless you are using them at the moment. Closing them out may free up enough memory to help prevent the lag you are talking about.
Also you may want to consider getting rid of McAfee; lots of people complain about its bulk munching on resources excessively. There are a lot of alternatives out there and some of them are FREE like AVG.
Norton is also a bulky resource gobbler.