As Lynn said, this is a nasty problem faced by all GUI programmers. The solution really depends on your program and what you need to show. I have documented one solution for one program here. While it does not handle the sorts of extremes you are handling, the techniques should be similar.
Another example you may want to look at is the NI-SCOPE Soft Front Panel. It does not scale the controls, but tries to maximize the area available for the plot. As a result, the main thing resizing is the plot. The controls just move around. If you have plots, this approach may work for you.
Finally, do not forget the large font issue. Vision impaired users will bump the font size to make things easier to read. A well designed program will be easily usable under these conditions. This will require active control on your part.
Good luck! If you have any specific questions regarding scaling particular controls or other such issues, let us know. You can scale most controls; however the method for doing so can be somewhat buried due to the high flexibility available to some controls (e.g. graphs and charts).
