im very impressed that you used Process Explorer to troubleshoot your problem. I see most forumers here never bother to even investigate the nature of the problem before asking.

Ive ran across several rigs with the same problem before and all of them seem to have this empty videos files or XVid installed. I would suggest that you disable video thumbnails preview and see if this fixes the problem.

And of course, ntdll doesnt mean anything because system drivers can be called by that process too. Use "xperf" from Microsoft to capture kernel hit count to identify the offending module.