Thanks, Shawn for your quick response. However, in my registry there is no key containing the string, "thumb." This may be due to the actions of a previous sevenforums volunteer who with my permission using TeamViewer altered my registry. So it seems that I'd have to create one or more new keys. I can do that, but I don't know which keys are needed and, further, despite the writeup to which you linked me, I'm not sure of the default value of MaxThumbSizePx (which I'd like to increase). I guess I've learned not to let well-meaning volunteers fool with my registry. In any case, the thumbnails seem to work fine now and I can easily live with the current maximum size.