Minimized file icon missing at task bar

Hi, everyone:

I have a strange problem with win 98 2nd
edition. After I open a file or web page and I
minimize it, usually it has a minimized icon on
the task bar showing how many files I have
open and running. But now the icons does not
show on the task bar any more. If I hold down
the ALT & TAB together, a separate window
will show up & show the icons of my
minimized files & home page. How do I
change it back or where to configure it, so it'll
show up on the task bar ?? I didn't see
anything on the Taskbar & Setting to make the
change. Any Idea ? Thanks.