TobyCat,
On your own computer right-click on a JPG file. Move the mouse pointer down
to the "Open with" item. XP will show a list of programs on your computer
which are capable of opening a JPG file. Your mother-in-law will have a
similar, if not identical, list. Ask her to click on the desired program,
for example, "Windows Picture and Fax Viewer".
What has probably happened is that the viewer selection was changed.
After she finds a choice which she likes then:
Repeat the above procedure but this time, under that list of programs,
click on the item "Choose Program ...." Have her highlight the viewer she
prefers, then ask her to click in the little box underneath the listing of
programs which says "Always use the selected program to open this kind of
file." After that, then click on the OK button and in the future the
selected program will open JPG files.
karl