You might have to reinstall Office. Alternatively, you could try opening up
the PowerPoint application and then going to the File menu and choose Open
to open up a PowerPoint file.
By the way, I assume you know this, but I can't tell from your message.
Windows XP is an operating system. Office contains the applications that
run files, such as .xls (Excel) and .ppt (PowerPoint) files. If you have
Windows, but you don't have Office, you will not be able to open .xls or
..ppt files.
--David
--
David M. Marcovitz
Microsoft PowerPoint MVP
Director of Graduate Programs in Educational Technology
Loyola College in Maryland
Author of _Powerful PowerPoint for Educators_
http://www.loyola.edu/education/PowerfulPowerPoint/