I have downloaded an evaluation copy of uVision, and now I will try to se if I can compile some old software written for Keil 4.20. But my software relies on a header file rtx166.h which is not present. Why is it so? Is it because it's an evaluation copy?
The RTX166 page tells you which products include it: http://www.keil.com/rtx166tiny/
See also: http://www.keil.com/demo/limits.asp
rtx166.h is not for the tiny model. The tiny model relies on rtx166T.h which I have.