Dell today made official its entry into the netbook market, with the Inspiron Mini 9, a $399 notebook that runs Windows XP Home.

The netbook will be available book through Dell and wireless carriers. The company is also offering a $349 version that runs Ubuntu. It should available in a few weeks time.

The Mini 9 packs in a 1.6-GHz Atom N270 processor, 512Mb of RAM, and a 4GB SSD in its default configuration. It also features 802.11g, Bluetooth, three USB ports, a 4-in-1 card reader, and a 32 W/hour battery. The screen is a 1024.x 600 8.9-inch LED-backed display. Users can expand the notebook to 1GB of RAM, an 8- or 16GB SSD, and can tack on an optional Webcam.

Also of note: an integrated 3G card that Dell failed to mention upon the device’s launch. Bonus!