Sounds like 2FastXP that was just renamed. 2FastXP was badged as being able to run off a USB stick. I never tried it because the developer's site said there were a ton of bugs - heeding him to go back and try to rebuild it again.
There should be a new release of 2Fast soon. Personally, I don't mind TinyXP Beast Edition. It works well, and has a lot of features (including wireless support) built into it. My old 800 MHz laptop with 128 meg ram boots up in 20 seconds with Beast Edition