Some companies allow cross-platform upgrades. Others don't.
This may help
http://www.tylernichols.com/apple/adobe-cross-platform-upgrade-how-to/"Early in 2007 I purchased the Adobe CS3 Web Premium addition for Windows because I was still using a PC for web development. Later, I decided to get rid of that system and go 100% mac. I was now left with the dilemma of what to do with my CS3 suite that I shelled out $1500 for. After some poking around the adobe website and making a phone call to customer service I found a solution. Adobe offers a “cross platform” upgrade for software owners who want to transition from Windows to Mac, or god forbid, the other way around. :p
Here’s what you do.
Call Adobe customer service and explain that you are changing platforms and you would like to exchange your registered product to the other platform version.
You will be assigned a Case Number by customer service and will need to pay them for the new media costs / shipping fee, which was $5 when I did my exchange.
After making payment, you will need to download a “letter of software destruction” form, fill it out and fax it back to adobe at 800-955-1610. Although Adobe doesn’t ask for the software back they do disable your old serial number as soon as you fax the LOSD form over to them. So no selling your old copy on eBay to make a few extra bucks. Another thing to keep in mind is that you will be without your Adobe product during the time it takes for your new software to arrive.
It takes about 2 weeks in total from the time you fax the LOSD to receive your updated software and new serial number."
also
http://blogs.adobe.com/jnack/2007/05/cs3_switching_p.html"CS3: Switching platforms, free upgrades
Q. Can I switch my product from Windows to Mac or vice-versa?
A. Yes. Just call Adobe Customer Service (800-833-6687 in the US; 020 7365 0733 in the UK; more country-by-country numbers here) for assistance. The process, as I understand it, involves signing an agreement stating that you've destroyed the product on one platform, and in return Adobe will send you the product for the other platform. According to the service folks, there may be a cost involved; verification of product is required; and restrictions apply. "