Unable to install UCS 3.3.0 from a USB drive

I downloaded 32-bit UCS 3.3.0 ISO file from http://updates.software-univention.de/download/ucs-cds/ucs3.3-0/ (I am stuck with a 32-bit server). The ISO file got copied to a USB drive just fine. The installation process also starts fine and I can get to the first step where I need to choose the installation language. However, the process is stuck at the next step complaining that no CD drive could be found. The machine I am trying to install UCS on does not have a CD drive.

Any ideas on how I can proceed?

Another user described the same problem, maybe the answer there can help you: Error installation UCS from Pen Drive