Error Installing Republic Commando

This is an image of the error I get when trying to install the republic commando. Either from ausgamers or fileplanet, both installers which I have downloaded generates the same error during installation (or even prior to loading the installer). It is enclosed in the attachment included in this post.

To me, it reads as if my service pack was the problem. By the way, I use firefox to surf & download my files.
But I disgress…

I have the same problem installing the Star Wars Galaxies 4-day demo from fileplanet, I have downloaded their 2gigs worth of a zip file two times (didn’t have the patience/determination to try a third time) and it’s always corrupt… What’s wrong?! Do I have a problem with Lucas Art’s products? All the full ones I have, though, work perfectly. I seem to have a problem only when installing a demo version from the internet.