Windows 8 is built for touch, and so is Dell’s new XPS 18: an all-in-one desktop that can also undock and be used like an 18.4-inch Windows 8 tablet. It’s very similar to the Sony Tap 20 that was unveiled last fall, but there’s one key difference beyond the display diagonal. The XPS 18 weighs less than five pounds — less than half what the Tap 20 weighs.Dell has posted few details about the XPS 18 on its website so far, but it looks like a pretty solid machine. According to Engadget, the XPS 18 base system features a dual-core Intel ULV processor and a 320GB hard drive to go with the 18.4-inch 1080p touchscreen. Other configs will be available, with processing options up to a Core i7 chip, as much as 8GB of RAM, and a massive 512GB SSD as options.Dell’s page does mention “excellent” battery life, but doesn’t provide the mAh or hours to back up that claim. Based on the dramatic drop in weight over the Tap 20, you’d suspect that the battery — generally one of the chief culprits in adding excess ounces to a device — will have shrunk slightly.The Tap 20 can only squeeze about two hours from its power pack before a recharge is needed, and it, too, utilizes an Intel ULV chip. That should be plenty for systems like these, and the XPS 18’s smaller display should give it a slight boost.When you’re ready to use the XPS 18 as a desktop again, Dell has multiple options for you. You can flip down the built-in kickstand or you can pick up a monitor-style dock to raise the XPS 18 up to a more ergonomic height. Dell’s also throwing in a Bluetooth mouse and keyboard, and you’ll be able to pick the XPS 18 up for as little at $900 when it goes on sale next month. The monitor-style stand will set you back another $50.