Ever since I installed Ubuntu 12.04 (maybe even before that) I had trouble adjusting the screen brightness for my Vostro3700. I tried a lot of different things to solve it but without avail until recently.

Finally I stumbled across the tweak in grub.conf with the appropiate video parameters.

I found my answer here

The two lines that got it working were these:

GRUB_CMDLINE_LINUX_DEFAULT="i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 quiet splash pcie_aspm=force "
GRUB_CMDLINE_LINUX="acpi_osi=Linux"

I have BURG and just in case modified burg.conf with the same parameters.