Originally posted by Ubuntu_user It could be that you have an academic version of CS3... I have CS5 extended I'd be willing to sell you since I upgraded to CS6. I'll send you a PM.
If you upgraded from CS5, he may not be able use yours to upgrade, especially if it was registered. I believe Adobe tracks the serial number from the old copy and if it has already been used in an upgrade, it won't let you upgrade another computer. I could be wrong however because Adobe has been known to do some strange things at times.