Hi and thanks for ur attention. For z500 lenvo laptop there is a problem with brightness key on windows 8.1 and windows 10; and each one has their own solution. Currently I have windows 10 and for solving the brightness problem you should do a manipulation in intel graphic driver and it's:
"Open this file and search "FeatureTestControl" and change 0xF000 to 0xF048 (or change it to 0xFFFF if doesn't work) [PwrCons_IVB_AddSwSettings] ------> [PwrCons_IVB_AddSwSettings] HKR,, FeatureTestControl,%REG_DWORD%, 0xF000 ------> HKR,, FeatureTestControl,%REG_DWORD%, 0xF048"
after this my the brightness keys worked perfectly fine then I installed Ubuntu 15.10 and when I pressed the brightness key in this operating system for the first time, everything got dark. and now when I login to windows 10 the brightness key won't work either and the only time I can adjust the brightness is before login into any of this tow OSs ( I mean in the boot page panel). and when I go to Ubuntu everything gets dark again but when I login into windows 10 it's same as the adjustment I just made before the login, but still I have no control on the brightness.
for solving the problem on Ubuntu I have tried these solutions in this topic: Make xconf configuration permanent but for each solution I got an error
Can anyone save me from this disaster , it's really driving me crazy and I'm new to Ubuntu.