According to HP ZR30w 30-inch S-IPS LCD Monitor - Specifications | HP® Customer Support your monitor has no HDMI port, but the Acer desktop has only HDMI ports?
You are probably using an incompatible adapter.
Thanks for your reply Stefan3D. I should have mentioned that. I use a Dual Link DVI-D adapter with my HDMI cable. I made sure the adapter is dual-link. I also tried with a different DVI monitor a 24" Dell LCD from a friend. This monitor has native resolution of 1920x1200. This time, my Intel Graphics panel showed resolutions up to 1920x1200. But when I re-connected the HP monitor, it was back to only 1280x800.
Hi Stefan3D, thank you for the suggestion about going the DP way instead of DVI. Unfortunately it did not work, but here are details.
It turns out most (almost all) HDMI-DP adapters are the reverse of what I need. They all help connect a DP source to a HDMI display. You are right, there are dozens of these available on eBay and Amazon for less than 5 USD.
However, they all mention that they are not bidirectional, and WILL NOT work if the source is HDMI and display is DP (which is my case).
After a lot of digging, I found one (yes, only one) such adapter on Amazon.
Here is the link above. It was a lot more expensive than the HDMI-DP adapters I mentioned earlier. But it clearly said that this adapter is for HDMI PC and DP monitor. It also has USB power to make it "active" So I ordered it.
Unfortunately, the result is the same as before. Intel Graphics recognizes the monitor correctly, but I still only get 1280x800 resolution.
I read somewhere that the wrong HDMI cable might be a problem. But in this case that is not the issue because the adapter comes with its own HDMI connection and cable.
Strangely, I tried the same setup (i.e. my new adapter and DP monitor) with a colleague's computer who had an HDMI card (nVidia GTX 650). This time, we could see all resolutions and set the monitor to 2560x1600, it's native resolution.