The present book contains a collection of the best papers presented at the 5th International Conference on Interaccion Persona Ordenador (IPO) (which is Human Computer Interaction in Spanish), which took place in th th Lleida on May 5 -7, 2004. This conference was co-organised by the Universitat of Lleida and the Universitat Oberta de Catalunya. Each year this conference is promoted by the Asociacion para la Interaccion Persona Ordenador (AIPO), the Spanish Human Computer Interaction Association, in collaboration with the local group of ACM- SIGCHI (CHISPA). In its fifth edition this...