Nobody at Bobcad knows anything about V21 anymore, they will register it IF you also have the newest version. At least in my experience. ( I have the advantage plan) Starting to really like the new versions better, V35 and V36. But I still have thousands of drawing on V21. When using V21 on an old drawing if I place the cursor on a line or point the geometry flashes and I have to hold there for several seconds before I get the tool tips flyout or can select the geometry. Very annoying. I am running Classic Shell on W10 think that might be it? Any help appreciated.