Lino,
First have a read here:
http://www.pptfaq.com/FAQ00253.htm
http://support.microsoft.com/kb/305040/en-us

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Luc Sanders
(MVP - PowerPoint)
>I have a PPT presentation stored in the hard drive which gave me no trouble
> at all. Recently however, when I open the presentation a box appears with
> the message "Microsoft Powerpoint has encountered an error and needs to
> close." PPT then closes restarts. This happens either at the beginning or
> after some slided in the presentation. I am using windows xp professional
> and Microsoft Office 2003 with all the recent updates. Please help