1.- I included in /boot/grub/menu.lst the following at the end of the line:
It increased brightness to 100%, about 40 or 50% more. But the sliding control disappeared from the GNOME Power Manager - AC Preferences, so I was not able to fine adjust the brightness, please see:http://library.gnome.org/users/gnome-power-manager/stable/preferences.html.en
2.- I eliminated from /boot/grub/menu.lst
Now the sliding control appeared at full 100% brightness, but the real brightness is about 50% no matter where I move the control, I do not understand this behavior, so no luck after hours investigating. I have spent various days with little sleep trying to configure my laptop, I am going to sleep tonight, I hope so.
I appreciate a lot if somebody can help me because I invested countless of hours investigating, I begin to lose hope in having a linux machine working, is becoming to long and stressful process. I guess I am almost done, but I need to see my screen well because I need to set up a lot of programs and my email accounts in PClinuxOS machine, webmail access is time consuming.
3.- I discovered gconf-editor so I think I can set the brightness to an appropriated value using the gconf-editor with root, if I have the parameters: acpi_osi=Linux acpi_backlight=vendor in menu.lst but if this works it will not be ideal, because at night I should change the brightness again.