Sony has announced its two latest additions to the Vaio range of notebook computers — its first notebook computer that can be used as a digital video recorder, and the smallest Windows XP notebook on the market to date.

The Vaio-U is the smallest Windows XP notebook to date, according to Sony. Measuring just 185x36x139mm and weighing 860g, the computer is noticeably smaller than Toshiba's Libretto mini-notebook computer. Like the Toshiba, Sony has chosen a Transmeta Crusoe processor, but here has gone for the faster TM5800 model.

The computer has 128MB of memory and while the TFT LCD is small at 6.4in, it offers XGA resolution (1,024x768). Other features include a 20GB hard disk drive, two USB ports, a four-pin i-Link IEEE1394 port, PC Card and Memory Stick slots and an Ethernet port.

Because it is so small, the machine is easy to hold with one hand on each side of the main body, gripping it with thumbs positioned on the top of the body just below the screen (pictured).

Sony has therefore included a number of design features to accommodate operation with two thumbs. Under the right thumb is a pointer, used to control the cursor, while under the left thumb are two buttons that mimic left and right clicking on a mouse. There is also a zoom-in button on the right hand side of the screen — something that might prove useful with such a small display.

Inspiration has also come from the world of mobile phones, where one-thumb operation for typing and sending email is so common it is becoming second nature for many.

The ThumbPhrase system makes use of a shadow keyboard arranged like that of a cellular telephone, with one button representing several characters or letters, which is used by the left thumb while the right thumb controls functions such as capitalisation or switching between the different Japanese kana and kanji characters.

The other machine, the Vaio C1, is based on Transmeta's TM5800 processor, which runs at 867MHz, has 128MB of DDR (double data rate) memory. It has a widescreen 8.9in display with ultrawide SXGA resolution (1,280x600), topped by a video camera with 350,000-pixel resolution.

The computer measures 249x28x152mm and weighs 998g. It can double as a digital video recorder, using an external TV tuner unit and the bundled GigaPocket software to record TV programs to its 40GB hard disk.

Sony has been bundling GigaPocket in Vaio desktop machines for some time, but this is the first notebook computer to include the software. The software has never been included on a notebook before because of the processing demands it puts on the machine. However, recent improvements in mobile processor technology, coupled with a hardware MPEG2 encoder chip which relieves the processor of much of the heavy work, have enabled Sony to do this on the C1.

Both machines were previewed in early March and are scheduled to go on sale in Japan on April 27. Overseas launch plans have not yet been decided, said Sony.

In Japan the Vaio C1 costs around £1,222 and the Vaio U costs around £800.