In May 2004, HP wanted to centralize all of its disparate North American ERP systems onto one SAP system. The cost of the project was estimated to be around $30 million and the ERP problems cost HP $160 million.
Mistakes made by HP
1) When the system went live almost 20% of the customer orders were blocked and had to be entered manually. This was because of data modeling problems between the legacy and SAP system, and it resulted in a backlog of orders. The connection between the legacy and SAP system were tested for both orders with customization and without customization, and they worked fine. The mistake was that HP did not test the all the different customer configuration, and hence some of the orders went through and some did not.
2) Customer service representatives were not properly trained to use the new system which resulted in more dropped orders.
3) The demand for configure to order system was 35% more than what HP had predicted, because of which HP had to buy a new factory in Europe. HP tried speeding up the delivery process for the backlogged orders which further increased the delivery cost by 35 to 40 percent.
All these problems were minor problems which could have been handled by HP, but since they all occurred together it turned to be a huge problem.
http://www.cio.com/article/2439385/project-management/when-bad-things-happen-to-good-projects.html