I have an HP Pavilion dm4-2033cl laptop (specs here) and am running ubuntu 14.04 LTS. I'm a professor and I need to be able to use my laptop on projectors in different classrooms (all apparently different models!) but so far it isn't going well.
I find that when I plug in to the projector by the HDMI cable, my resolution drops down usually to 640x480, a bit bigger in one classroom. When I plug in by the VGA cable, the resolution is fine but the option to "mirror displays" is grayed out and I have to treat the projector as a second screen (i.e. turn my back to the students to give my demo).
I think this may be a clue to the problem: When I go to Settings -> Details, the "Graphics" card is described as "Intel(r) Sandybridge Mobile". However, I know from HP that I have an Intel HD Graphics 3000 card. Does this mean I have the wrong driver, and could that plausibly be the problem? If so, how would I fix it?
This is the video card described in the output of lspci -v:
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA controller])
Subsystem: Hewlett-Packard Company Device 1650
Flags: bus master, fast devsel, latency 0, IRQ 44
Memory at c0000000 (64-bit, non-prefetchable) [size=4M]
Memory at b0000000 (64-bit, prefetchable) [size=256M]
I/O ports at 4000 [size=64]
Expansion ROM at <unassigned> [disabled]
Capabilities: <access denied>
Kernel driver in use: i915
I think your drivers are fine (Sandy Bridge seems to a broader name for your card as you can see here)
Just in case, check that your system is up to date (run
sudo apt-get update && sudo apt-get upgrade)If the problem persist, you can try to reinstall the drivers as explained here.
However, for me this smells more like a bug. I hope other users come by and help you.