3DSprite Photoshop (on the Mac anyway) requires 15 - 20 MB RAM for the program PLUS 3 to 5 times the RAM size of the picture in order to be able to do everything in RAM (there are at least two filters that MUST have the RAM or they won't work at all! They are the displacement and lighting filters). If that much RAM is unavailable, PhotoShop will attempt to use the hard drive (or whatever drive you have specified in the preferrences) as RAM. The more RAM you make available to it, the less time you will spend watching the little progress bar inch it's way across the screen. I personally have allocated 250MB RAM to PhotoShop and most operations happen very quickly (average picture size is 7MB - 20MB). -Jim