Microsoft has released a great utility that you can use to monitor all of the process/threads running on your machine.  It's great utility to figure out what's causing your machine to run slowly.

Here's the description of the utility:

Process Monitor is an advanced monitoring tool for Windows that shows real-time file system, Registry and process/thread activity. It combines the features of two legacy Sysinternals utilities, Filemon and Regmon, and adds an extensive list of enhancements including rich and non-destructive filtering, comprehensive event properties such session IDs and user names, reliable process information, full thread stacks with integrated symbol support for each operation, simultaneous logging to a file, and much more. Its uniquely powerful features will make Process Monitor a core utility in your system troubleshooting and malware hunting toolkit.

Process Monitor runs on Windows 2000 SP4 with Update Rollup 1, Windows XP SP2, Windows Server 2003 SP1, and Windows Vista as well as x64 versions of Windows XP, Windows Server 2003 SP1 and Windows Vista.

Here's the site that you can go to download it (see bottom of the page): Click here

Enjoy,

~Robert Shelton