OpenCV Object Detection Howto:
By Florian Adolf ( robotik [at] inflomatik [dot] de )
How-to build a cascade of boosted classifiers based on Haar-like features
Download the pdf file which explains 'how to' in windows..: OpenCV Object Detection
The tool "objectmarker" mentioned in the tutorial can be obtained here. To convert the directory with subfolders 1..n to a xml file use the haartraining archive provided in the files section of the yahoo group.