The last 15 years have seen the emergence on the software market of a category of software called Enterprise Resource Planning systems or ERP, which has become the focus of both researchers and practitioners in the information systems area. At this time, the ERP software market is one of the fastest growing markets in the software industry with long-term growth rates of 36-40%. Some estimates put the eventual size of the market by the year 2010 at US$1 trillion (Bingi et al., 1999). Since these estimates have been put forward, the ERP market has slowed down, but the overall growth of the enterprise-wide application market is still quite strong, thanks to a number of additional segments, such as Customer Relationship Management (CRM) and Supply Chain Management (SCM). Also, more recently, a new trend is emerging in the market: the re-implementation and extension of ERP, referred to as ERP II (Humphries and Jimenez, 2003).