Just how small can PCs get before they become unusable? Mobility is one of the big themes at Computex this year, and manufacturers are battling to outdo each other in producing the smallest, coolest PC. But I'm starting to wonder whether some of them are just for show!

Certainly, the devices launched at Computex are impressive, with new models from Asus and Via amongst those worth a look. Asus’ Eee PC has a 7in screen, weighs under 2lbs and can boot in seconds from flash memory. Asus says the product will cost just $199 with a Linux OS, although a more expensive Windows XP version could also become available.

See our first-look review of the Eee PC.

Via, meanwhile, has launched the Via Nanobook – a Windows XP/Vista-based portable weighing roughly the same at the Eee PC and featuring a 7in screen, 30GB or 60Gb hard drive and a 1.2GHz processor.

These systems may have been inspired by One Laptop Per Child’s drive to put together ultra-portable, ultra-cheap computers for emerging markets. But unlike OLPC’s so-called $100 laptop, but both the Eee PC and the Nanobook could become available in Europe too.

And manufacturers at Computex say we haven't seen the end of PC miniaturisation. Via, which is demonstrating the business-card sized Mobile ITX motherboard, said it plans to produce even smaller form factors in the coming years, combining the PC chipset with the CPU to save even more space. That could give hardware partners even more flexibility to produce smaller PCs.

However, others at Computex are questioning the demand for a plethora of miniature PCs. A spokesperson for one manufacturer which is showing off a UMPC design said it was still unsure whether the platform would take off in a big way and warned that the future of extremely portable PCs remained unclear.