One of my co workers Chris Henley just did a great video/screencast on WinPE. What is WinPE?  Have you ever done custom setups of Windows? Have you ever needed a small version of the OS to boot a box and troubleshoot hardware issues?  Yep all of that is WinPE.  It's part of the Windows Automation Installation Kit (WAIK).

Go check out Chris' video http://blogs.technet.com/chenley/archive/2008/08/27/custom-win-pe-images.aspx

Chris shows you step by step how to do this!  Great 17 minute video!!

And download it here:

http://www.microsoft.com/downloads/details.aspx?FamilyID=c7d4bc6d-15f3-4284-9123-679830d629f2&DisplayLang=en