Dear Eric, I just join the Chimera-users discussion group and haven't got reply email. However I checked the archive and found your reply email related to the WinXP SP1 python error on File -> Open. I have been using Chimera to generate the colorful ribbon picture for the pdb file using command line. Now I am tring to figure out the general way of defining the bfactor range corresponding to the different colors. I found the flexible python code for making the rainbow color by bfactor and tried it out. But it ended up with the file/open error message as I didn't see any problem in the code. Attached please find the copy of the python code. I did replace bo and b1 by min and max of bfactors in the pdb file. Your help and suggestion are greatly appreciated. Li Wang Biomedical Informatics of OSU Columbus, OH (w) (614)688-3236