The Sony pen tablet computers models PCV-LX 900, 910, 920 featured a 1 GHz Pentium III processor and 512MB maximum RAM. They can be upgraded with PowerLeap processors to 1.4 GHz, but then they run a much noisier fan.
In my opinion, these models support the best pen tablet display available, especially because the stand provides the most ergonomic adjustability of any similar monitor.
On Sony's Japanese website, I found more advanced models of this great computer. In particular, they made a model PCV-LX96G which had:
Windows XP Home, a Pentium 4 1.80 GHz, 1 GB Max RAM, 80GB Hard Drive, a DVD-RW drive, and a Giga Pocket video I/O card.
http://www.sony.jp/products/Consumer/PCOM/PCV-LX96G/
There are really good pictures available here:
http://www.vaio.com.tw/news/news.asp?id=189
All the websites (at least in Google) that refer to this model are in Japanese. Does anyone know where this model could be obtained, and whether English documentation might be available? The finder's fee will be provided.