Download Piriform Speccy.   It is made by the same company that makes CCleaner.  I happen to have that on my system and when I run it it shows both graphics cards.  I have the 1.5GB version and it shows 1536MB.  The other option is to run something that would use the 555 then run cpu-z while that program is running.  Then in the graphics tab for cpu-z you will be able to select the 555 from a dropdown menu.  Cpu-z will recognize it once the graphics are running.  The easiest way to make sure the graphics are running is just right click on your web browser icon and select "Run with graphics processor" then "High performance NVIDIA processor".  That will force your browser to open using the NVIDIA, so while that is open use cpu-z.   I have tried doing the "Run with graphics processor" directly on cpu-z but that doesn't seem to work.

and let me add that this is a VERY SERIOUS problem, since some game DO NOT recognize the video card just as Windows! for example: GTA4 , DEMO PES 2012.....

very interesting topic, I wanted to try too