Free-form writing on a touchscreen at any time with Win8

Question

How can I configure a Windows 8 computer with a touchscreen to let me write notes on the screen at any time, right "on top" of whatever else happens to already be on the screen? Basically, I'm envisioning a layer that acts like an overhead projector transparency (remember those?), and a stylus or finger as the marker.

My use case is making notes for myself during videoconferences, so programs that only allow writing on blank pages or certain limited forms of pre-loaded files (e.g. PDFs) won't work for me.

I don't care if this is supported natively or by some third-party app/program or what.

Answer 1

I didn't mean for this to turn into a software recommendation question, but I ended up using the third-party product Ink2Go.

Answer 2

The free ScreenMarker works (rather simplistic), but the behavior is bit confusing (clicking the clear button doesn't immediately clear the annotation until another annotation). This is just one of the various "on-screen annotation" apps, you might find other with more feature if you need them.