Naveed has discovered a vulnerability in Microsoft PowerPoint, which potentially can be exploited to compromise any user's system. The vulnerability has been confirmed on Windows XP SP2 with a fully patched PowerPoint 2003. Other versions may also be affected.

The vulnerability is caused due to the application using data taken directly from a PowerPoint presentation file as a pointer when saving or closing the presentation. This can be exploited to corrupt memory and manipulate the program flow in various ways.

Successful exploitation crashes the application and arbitrary code execution may potentially also be possible, but has not currently been proven.

via Link

There isn't much you can do at this time other than to follow the old advice - Never open email attachments from strangers. You also also consider switching to Open Office suite.