Thread
Connectix Speed Doubler and RAM Doubler
I seem to remember this happening and finding that their protection system is pretty low-tech, it just looks at the name of the disk (which can be a mounted image as they look the same to the system) so you have to give your image on the desktop the same name as the original discs (I expect someone will know what that name is, I haven't got my downloaded image to hand).
The disk name for RAM Doubler is simply "RAM Doubler" . The Speed Doubler one is almost certainly just "Speed Doubler" . Admittedly my RAM Doubler installer is 1.6.2 so it may be older and more basic than yours.
If this doesn't work try duplicating the disks and running the duplicates. Might make a difference.
If this doesn't work try duplicating the disks and running the duplicates. Might make a difference.