I, and a lot others have been runngin cs3 on 64bit os (vista) and I have no problems myself. Others have stated they have problems, cs3 is not officially supported. So it's up to you to find out. I would suggest if you have it, a spare drive to install and load 64 os on it and then install cs3. (pull your original drive out for the duration.that way, if you run into problems, you still have all your original setup on your original os drive.