There is a very good chance that you are attempting to deploy a version of Flash Player (or any free Adobe product like Acrobat Reader, AIR, etc) that was not meant to be deployed.
Adobe doesn't allow the download site to be posted on a publicly accessible site. In order for you to obtain the link to download a version of Adobe Flash Player that can be deployed please visit http://www.adobe.com/products/players/fpsh_distribution1.html and submit the necessary form to Adobe. They are usually pretty good about responding quickly.
If you are attempting to deploy a valid, for distribution, version of Flash Player AND you get the 1603 error, chances are that your AntiVirus software is preventing the installation from taking place. Make sure that you have an AnitVirus exception for the following directories (based on your version of PDQ Deploy)
PDQ Deploy 1.5.x - %WINDIR%\PDQDeployRunner
PDQ Deploy 1.2.9.x - %WINDIR%\PDQDeploy
PDQ Deploy Pro 1.4.x - %WINDIR%\PDQDeployPro