As an answer to your question about using CS2 with OS X 10.5...
If you upgrade to 10.5, it's very likely that your CS2 will stop working. Adobe never provided an update on much of their older software which _was_ working in 10.4. There's lots of info about that here:
http://www.adobe.com/support/products/pdfs/leopardsupport.pdf
That Adobe article has a title about CS3, but lots of older Adobe software is noted in that document.
I agree with MisterMe - especially about the heavily-advertised MacKeeper, (seems that you get MacKeeper when you download the title "Mac Cleaner")
Will something happen if you use it? probably (and you likely won't be able to choose if the result is good, or bad)
Will I trust it to work correctly? As a service tech, I haven't had any experience with that software that gives me any confidence in it.
If you do decide that you need some system maintenance, stay with apps that actually have a good history, such as OnyX, or YASU.
Also, MacKeeper (which, BTW, is Intel only) is not free ($40, I think), and I think good results with free software is much better than the great feeling that you get when your file system is trashed by some software where you actually paid real money to do some task that is otherwise free.