Microsoft offers Process Monitor as a free download. In short, this tool helps capture detailed events and isolate issues. I recently used Process Monitor when I encountered a performance issue with one of my portals; the default.aspx page was taking a long time to save. Process Monitor helped me isolate the issue and determine that the cause was a buffer overflow.
Microsoft (2010). Windows Sysinternals, Process Monitor v2.91. Retrieved July 6, 2010 from http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx