Finding problems such as what you indicate may be hard, depending on of course of what is actually hanging it. Many things can cause a system to pause while it indexes or searches or checks or goes online or whatever.
The biggest thing you can do it to make sure you are aware of what is happening when the system stalls. Is the Hard drive running, any network traffic, or other system indications.
If you Open Task Manager and watch the Processes tab (watch all users), it may give an indication of what is taking the cpu time. If you can find something there, perhaps we can track it down. It is best if anything you want to use to monitor is open before a problem occurs.
If you check the Event Viewer, do you notice any repeating...