OK, I'm assuming this is a Windows version of CS3 that you are trying to install on Ubuntu, which is a Linux based OS.
If that is the case you should know that Linux is not Windows, Windows applications do not run on Linux or vice versa!
At least not by default anyway....
If you install Wine, which is basically a Windows emulator/compatibility layer (Search for it in ubuntu's package manager or the software centre) you can install and run some Windows applications on your Linux box.
But be warned, it doesn't work with every Windows program.
The Wine projects website lists lots of programs that will run properly under Wine and also lists configuration options to improve the performance of some applications that don't run quite so well.
I'm not sure if CS3 will successfully install or run under Wine in Linux, you'll have to take a look at the wine website, or try it for yourself.
Otherwise have you considered using any free / open source alternatives to CS3 on Ubuntu??
For example instead of Fireworks or Photoshop, you could try Gimp.
Instead of Illustrator you could try Inkscape. Instead of Flash, you could use the free Adobe Flex SDK.