If you don't want to pay Microsoft tax and want an Ubuntu pre-installed PC, ASUS Eee PC 1225C is the machine you are looking for. Amazon has been selling this device since March 2012 for $422.

The notebook is powered by the new Intel Atom Cedar Trail processor and runs on Ubuntu 12.04 LTS.

The hardware specs are:

• Display: 11.6" LED Backlight WXGA (1366x768) Screen
• CPU: Intel Atom N2600 (Dual Core; 1.6GHz) /N2800 (Dual Core; 1.86GHz) Processor
• Memory: DDR3, 1 x On Board Memory, 2GB
• Storage: 320GB/500GB HDD
• Wireless Data Network: WLAN 802.11 b/g/n@2.4GHz
• Bluetooth: V3.0
• Camera    0.3 MP Camera
• Audio    Hi-Definition Audio CODEC
• Stereo Speakers
• High Quality Mic
• 2.2Ah 6 cell target: 7.5hrs

One point to be kept in mind is that the RAM is that it is soldered to the board so you can't replace, repair or upgrade the RAM.