well, i don t think its about the legality of the product - i use a legal version of photoshop CS3 ( shared copy from the university that every student in the class is allowed to use - arts/design class ) - and it crashes regularly with either a CTD or a simply "does not respond anymore".
photoshop 7.0 works much more reliable - so if you have an earlier copy of photoshop you may just try that. - personally, i have given up on photoshop CS3 and i m back at 7.0. most of the features that CS3 offers is only used when you re a professional anyway - for casual use, 7.0 offers more than enough features.
Try this. Under I believe Edit, there is a command named "purge all" click that, it will ask you if you are sure, just click yes. Photoshop will "lock up" for a few minutes, it may even shut off. After that, bring it back up if it closes or continue on as needed if it stays open.
What is does is purges all data that has been used in Photoshop for whatever reason, some of the data stays in there and causes havoc on the program. Give that a try and see if it works.