Office XP Word Icons Disappear from Taskbar

[Bob]

I have a computer running Windows 2000 Pro SP4 with Office XP. After
working with several Word files I minimize each one as I work. I check
e-mail and other items. After a short time, not sure how long, the Word
icons disappear from the task bar. No where to be found. I then open Word
and if I check what files show in the list under the menu item Windows I see
my files and can select them.

Is there anyway to fix this so the Icons do not disappear? It is really
annoying that I have to open Word again to find my files that are already
open.

Thanks,
Bob