cs3

I'm running CS3 on Mountain Lion with no problems. Are you sure you don't mean CS2? Some people have interprited that as "free" but it's not compatible with Mountain Lion and can't be used.

What free CS3 download are you refering to (downloads are usually free, but beyond a trial period the use of the software is not)?  How old is your operating system?

Hi,

What exactly the issue you are getting while installing CS3. Also CS3 is not tested on Mountain Lion so compatibility could be the issue.

System requirements for CS3

http://www.adobe.com/store/en_us/popup/software/creativesuite/mastercollection/systemreqs.html