Microsoft recently released a tool called 'Process Monitor', which is an enhanced version of the Sysinternal Process Explorer utility (which has been retired). Microsoft recently acquired the Sysinternal web site and tools, and hired its creators.
Process Monitor is a great utility for performing advanced system monitoring and getting real-time file system, Registry and process/thread activity. The utility now incorporates the features of two other Sysinternals utilities, called Filemon and Regmon.
Process Monitor runs on Windows 2000 (SP4), XP (SP2), 2003 (SP1), and Vista. Its also supports both x86 and x64 versions of Windows. Check out the web site for more information