Mac applications are a little different than the Windows ones. For example, if you change the OS, Windows might attempt a possible launch of an old version of the software that wasn't developed to be compatible with the current version of OS. It's called backward compatibility and it works for most of the Windows versions. For Mac, it's different. For example, if an application was developed for SnowLeopard, then it will work for almost all versions up to SnowLeopard. Lion will refuse to run the application. Besides that, there's no compatibility tweaks. My advice is to obtain a new version of the software from the one you've purchased it.
