File extension association.

Hi

I am very new to PortableApps platform and just wana ask a basic thing, if I put portable apps suite including open office on my usb drive and then, I go and try to open a .doc file, it doesn't open in open office, it opens in default Microsoft Word installed on the system, or doesn't open at all if the system doesn't have MS Office installed.

Is there a way to associate doc to open office on thumb drive? Or would I have to launch OpenOffice Writer first and then open the file manually?

Thanks a lot.

-
Raman