Here's a formula to make a fortune: take an old product, work out what originally drew consumers to it, then recapture that feeling while adding a little more panache. Apple went through that process with online music and eBay did the same with internet auctions. Amazon.com has done it with its electronic book reader, Kindle. It is now the laptop's turn to undergo a makeover. In a trend known as 'liliputting', the notebook PC is becoming so small you can prop the device on the outstretched fingers of one hand. The market for the compact , low-cost 'ultra-portable' - also known as 'sub-notebook' - seems set to explode, helped by the increasingly clunky look and feel of standard-size, conventional laptops. Every time I place my old notebook on a desk, I find myself increasingly tempted to consign it to the gadget graveyard. My legs get barbecued whenever I lay the device on my lap, thanks to its hot, power-hungry Pentium processor. When I take it to bed and go online via Wi-fi, my back aches because I cannot cradle the machine like a book. Its three-hour battery life is nothing to write home about either. So much for the laptop's touted convenience. With the new breed of ultra-portable notebook computers, much of this aggravation evaporates. You can read your mobile marvel like a book and carry it easily in your handbag, or 'man bag', without setting fire to the contents. True, ultra-portables do not come with all the bells and whistles. Essentially, they consist of a small display, a keyboard, a hard drive and a sprinkling of vital data ports. But these machines have a longer battery life - about five hours - and are 'expandable'. When more capacity becomes essential, you can connect extra drives with a USB cable. The result is a slim, lightweight device that is as easy to carry as a keychain camera. I am more attracted to ultra-portables than any model of smartphone or satellite-based car-navigation system on the market. I had an initial aversion to these devices, following a 'mini-computer' demonstration conducted by a prominent technology company several months ago. To me and the other assembled reporters, the machines simply looked like squashed, chunky laptops - about as inspiring as a stale sandwich. But I am so utterly taken with ultra-portables I feel ready to enter my old-fangled laptop into Wired's 'destroy-your-most-hated-gadget' gallery, as did Treo-basher Dan Tentler ( www.wired.com/gadgets/miscellaneous/news/2008/04/submissions_gadget_abu… ). The same fate awaits my personal digital assistant, which carries more bugs than a doss-house mattress. I may soon invest in a sub-notebook from Asus, the brand that seems to have single-handedly propelled this niche market into the spotlight and remains its frontrunner with the Eee model. But as the form-factor infatuation strengthens its hold on gadget-hungry minds, the market is becoming competitive. Other brands to conjure rival devices include the Everex Cloudbook, Sony's Vaio TZ series, the Northec Gecko and the Hewlett-Packard Mini-Note. Aside from various gremlins and glitches that bedevil all computers, the lone snag with sub-notebooks is the size of the keyboard. Small keys need nimble fingers.