I was involved with supporting users of these PC's, and also in developing quite a lot of software for them. I still have a soft spot for them.
The original HP150 has a rather small screen and a series of holes around the bezel of the screen to let the IR beams through. In the dusty environment I was working in, these would get clogged with dust and the touchscreen would become unreliable.
Our first solition was to squirt freon into the holes. This tended to blast most of the dust out, but was never a really good solution.
A friendly HP tech showed us how to partially dissasemble the HP150 to get at the IR assembly and give it a thorough cleaning with copious amounts of freon.
HP also brought out a little plastic thingo which covered to bottom holes. (but kept falling off)
We discovered the easiest and cheapest solution was to simply cover the bottom holes with clear adhesive tape.
Soon after the Touchscreen II came out with the larger screen and rather more sensible IR transparent plastic bezel.
I also still remember that a replacement keyboard was listed at $600
p.s. Oooh! Just read the "Terms of use". Two thumbs up from me!