I've been searching on the internet for some kind of tutorial to do this and I've only found this one that seems to do the work ( http://tech.nabtron.com/add-custom-field-for-user-data-joomla-1-0-tested/97/ ) but the problem is that this tutorial is focused in Joomla 1.0 and I'm using Joomla 1.5.. the files are not in the same place and some classes are very different...
It will be great if you could point me to a web page where somebody explains how to do this.. Or if you are a Joomla expert help me with this please... I have some knowledge about php and mysql but I'm not familiar with the Joomla workflow.
Any kind of help will be much appreciated.
Thanks everybody!