Why does my gmail email only download to one or the other of my PC's?

I doble checked and both PC's are configured the same. Depends on
which one checks the mail first as to which one gets my gmail. Both
PC's are running Outlook 6.0 and both are configured to leave all the
mail on the server for 5 days.

What can I do?

Try changing your Gmail setting (not Outlook) to keep Gmail's copy in
the inbox when messages are accessed with POP.  This setting can be
accessed in the "Forwarding and POP" tab of the Gmail setting.

not exactly an answer to how to fix it but insight into why it happens:

a lot of e-mail services push the e-mail onto your hard drive as soon
as the e-mail hits you mail box (opened or not) this saves the storage
space on their server.