Hi Helen,
Since I haven't heard back, I think I'll be returning the concrete prep tool to Home Depot this evening. It's $130/day for the disc + the machine itself, and it would need to be back in tomorrow morning by 9am anyway. If you want to give it a go in the basement, you can just rent it for another day yourself at whatever time works best for you. I was able to transport the thing myself, in the passenger seat of my small car, from the HD in Oakland (Emeryville doesn't seem to have tool rental).
I successfully finished doing the floor in our storage/lab room, but I recommend that we look for a better solution to do the main floor in CCL - possibly hiring some professionals that may have tools that do a much better job at containing dust. This prep tool also doesn't deal with crusted-on chewing gum well (and this storage room used to be the green room for the heavy metal bands that came through here in the 80's and 90's...), so I had to scrape most of it off by hand, and then go over it again with the tool - ugh.
No idea how well it would deal with the paint on the floor in the basement...
Patrik