I have a friend who has Vista operating system
That's not relevant.
and when I send her power
point presentations (previously sent to me)
PowerPoint presentations are files created with PowerPoint (or some
compatible program), and to view them, you need to have PowerPoint (or
some compatible program) installed. Since you have been able to view
them, you apparently have what you need installed.
she says her system doesn't recognize them.
It's not *her system* that doesn't recognize them. Almost certainly
she simply doesn't have PowerPoint (or some compatible program)
installed.
If she wants to see them, she needs to install something suitable. She
can buy PowerPoint, but if she just wants to view PowerPoint
presentations and not create any herself, she can download and install
the free Microsoft PowerPoint viewer at
http://www.microsoft.com/downloads/...40-14e1-467d-8dca-19d2a8fd7485&displaylang=en
or
http://tinyurl.com/yyzosw