I experience occasional 'freezes' on my desktop machine (Windows XP SP3). I've tried the normal debugging methods I know (watching Process Explorer, running ProcMon (hard to get a good trace because the hangups are so intermittent).

Are there any additional system debugging methods that might be useful in discovering what would cause these hang ups?

While this question is more about debugging methods than the actual issue itself (which is probably more of a superuser question), the symptoms of the hangup are:

• All windows become non-responding. Can be brought the foreground, but do not repaint.
• Taskbar/explorer windows are non-responsive
• Ctrl+Alt+Del, Ctrl+Shift+Esc, Win+L, do not do anything (though the actions are queued up, and when the system unhangs, they are performed)
• Oddly enough, usually I can still scroll through the current page I have open in Google Chrome, but I cannot change tabs.
• Hangup can happen when I have tons of apps open, but also when I only have Outlook, Chrome, and MS Communicator (plus all the corporate spyware).
• Usually the hang lasts between 30sec and 3 minutes or so. After which I can continue working as usual.