I teach at a community college, lecturing daily with slideshow presentations (which mostly originate from the textbook publisher). The classrooms where I teach have a lectern computer with an overhead projector.
Unfortunately, the lectern computers were all installed in a way that they only have a single video output, and the projector can only show a duplicate of what's on the lectern monitor itself. (My understanding is that a cheap video splitter was used instead of two separate monitor outputs.) Therefore, it's impossible to make use of the standard slideshow-presentation "presenter view" feature (where the audience sees one thing on the projector, while the presenter sees notes, upcoming slides, timer, etc. on the lectern monitor).
I've inquired about getting this fixed numerous times, going back over a decade now. I'm possibly the only person in my department who uses presentation slides -- it's still considered novel and unusual -- and I don't think anyone I've ever spoken to understands what the issue or "presenter view" is. So, I see no sign that the hardware issue will be fixed.
Thus, I'm looking for some way that I might be able to jury-rig an effective second monitor temporarily while I'm class. I have access to the computer tower under the lectern, and can plug in USB devices as needed (routinely use a memory stick, digital clicker, etc.). I don't have access to the monitor cables (padlocked at the back of the PC tower). I have my own tablet, laptop, etc. that I could bring and plug in. The school towers all run Windows. The lecterns have MS Powerpoint locally installed; but I normally I run slideshows via Libre Office Portable Impress from a USB stick. The lecterns do not have the Miracast wi-fi screen-casting software available.
At this point, I'm personally stumped. What options are there for me to plug in another device here, and get the functionality of the slideshow "presenter view", with different image on instructor monitor vs. overhead projector display?
Update: It turns out that the "cheap video splitter" story that I'd been told by IT staff was not actually correct (nor something I could verify, the way the towers are locked in place with the back inaccessible). The selected answer shows how to access the existing projector as an extended monitor in Windows, which apparently no one at my institution knew to explain.