So does anyone know of any workaround for this? I know I can tape over a pin on the HDMI connector to disable the autodetect feature, but DisplayPort connecters have much less room for that, and Mini DP-forgettaboutit. If my primary is connected via DP and I turn it off, the primary desktop moves to the secondary monitor and rotates sideways so that it's back to landscape mode. Here's a hilarious example of it misfiring: my secondary monitor is in portrait mode next to my primary. But it's not so great for stationary desktop setups that just so happen to use DisplayPort connections. I get why it wants to do this: if you connect a projector or TV into your laptop, then files and windows won't get orphaned on an unviewable portion of the desktop until you reattach it. If a monitor is plugged in via DisplayPort (and supposedly HDMI too, but I've never used it), the extended desktop associated with that monitor will disappear when that monitor is turned off. So, I have a problem with monitor autodetect in Windows.

Autodetect nvidia