That was the TC1100 - one of the only hybrid slate tablets of its day. It started out as a Compaq product and became HP after the merger.
I had one and it got me through 6 years of electrical engineering. I still believe it was the best machine of its day for students because of its weight, size, build quality and versatility. It was very expensive for its performance but to me it was worth it. All said, though, the performance was quite good if you kept it clean. I ran Matlab, did PSPICE simulations, some light CAD (hooked to an external mouse and monitor), not to mention taking hundreds of pages of handwritten notes and running all the standard MS Office crap. Seriously there wasn't a single thing I threw at that machine that it failed to run. Not to mention that in the whole time I used it I don't recall having a single blue screen. My brother lusted over the machine so when I graduated in 08 I gave it to him. He still has it.
I also believe it was one of HP's worst marketing debacles ever. I swear it NEVER failed that when I sat down in a populated area and pulled out that machine and opened it up at least one person if not more would come over and ask what it was...and by that time it was already discontinued. Nobody had ever seen it. HP marketed it to managers and doctors and it ended up being a failure.
I always felt HP should resurrect the TC1100 in slimmed down trim with updated internals and they'd have a winner (if it was done right). But alas...HP has chosen to chase others rather than lead. This was just another opportunity to offer a unique product that would set them apart and they squandered it...again.
There's still a following for the TC1100. I bet when Windows8 comes out people will be slapping that on them...and I bet it will run great.