Software Deployment

I'm working on SAS Cube Studio 9.1 and there is a service pack i need to install with it. The problem is that when i try to install the service pack using a network image of the CD i don't even get the option to install the service pack, but if i run the setup from the CD itself , it installs fine with the service pack. Does anyone here know how i can trick the installer to believe every time i launch the setup it's from a CD or know of how i can get around this.\

thanks in advance for your feedback.