Problem faxing office documents

Hi all,

This is what I am trying to achieve. I am writing a web application to allow
my users to submit their documents for faxing. I have tested it using bmp and
txt file and both seems to be ok. When I try to test with excel of word
document, it gives me error. From the applicaiton event log, noticed that
there are some messages on msiinstaller couldn't find some keys in the
HKEY_CURRENT_USER registry. From the task manager I noticed that winword.exe
or excel.exe was run by Network service (I am using Win2003 server). So, I
changed the user identity that run the defaultapppool in my IIS with a userid
which I can login and launch Word or Excel(I thought it's because there's
some registry settings that needs to set during the first time using office).
But even after that when I ran the application again, it gives me the same
error. The problem only goes away when I add that userid into administrators
group which I am not infavour of.

Can someone enlighten me on this?

Thanks in advance