If you take a look at the application (or system) event logs, we might get a
better idea on why it is failing. The reason why is that Office/Outlook
2003/7 build a hidden folder on a local hard drive named MSOCache. This
cache folder is called the Local Installation Source (LIS) and there could
be something wrong with it rather than what you have (or don't have) stored
on your jump drive. If this folder is kaput, then Microsoft does have a
toold that can remove it correctly so that all future requests for repairs,
feature add, .etc will need the installation media. If curious about this
tool, use your favorite search engine and search for 'LISTool'.
I only have one copy of MSMAPI32.DLL and it is at the location I gave. As
for MAPI32.DLL, I have two. One is in \windows\system32 and it is the one
that shipped with the operating system (XP in this case). The other is at
the location I gave and ships with Office/Outlook. Microsoft Outlook 2003/7
use the one under program files.