There are numerous instances of things going wrong when installing new programs, especially if the program requires a more in-depth installation than a simple drag and drop to the Applications folder. Sometimes missing or corrupt system components will not properly check out with the installation utility, or you may be using a package that is not built for your computer's architecture (running PPC or Intel-only applications on the opposite platform). Other times, however, the problems people experience are not caused by the operating system or application software at all.
We were contacted by a new iMac owner "Allan" who recently switched from Windows and needed to install Adobe's CS5 suite to run both Photoshop and Indesign. The suite seemed to install just fine but when it got to the point when Photoshop or Indesign were being installed, the installation media would eject with an error stating the installation could not complete.
Naturally the first instinct is to look at the OS setup and blame the issue on some fault with the OS. When I heard about this I suggested using the Console to check for error messages, using Safe Mode when installing, and finally reapplying the latest combo updater or reinstalling OS X. Besides these suggestions, Allan also had tried PRAM resets, among other common tweaks to get the installation to work, all without success.
Even Adobe representatives he talked to mentioned they were unsure what the problem was, and blamed the Mac OS on the problem.
At this point everyone was thinking about the terms of the OS and software, and figuring there was an incompatibility that was resulting in the issue at hand. However, it turns out the problem was not with the computer or Adobe's software at all. Instead, the issue was with faulty installation media, which was discovered when Allan decided to try downloading the trial versions of the applications that would not install from the DVD, and instead installed them from the disk images. The installations went fine and he was able to register them to full working versions with his previously purchased license keys.
Sometimes individual DVD drives may have difficulty reading some media--even commercially pressed discs--so while the media may appear to be fine, your drive may not work well with it. While using downloadable installers is one way to tackle faults with media, another way you can recover the media is to create your own disk image from them using Disk Utility, Toast, or another utility that's capable of these functions. Even though an installer may not be reading from the disc properly, burning utilities may have a more robust reading routine that can read through the faulty area of the disc. In addition to creating images, you can also try directly duplicating the DVD to another one either with the same computer or with another one.