This package, when installed, will give you OpenOffice.org, AbiWord, the IceWM window manager, Firefox 3.0 (called Iceweasel in Debian) with Java support, printing support, and access to thousands and thousands of applications that can be easily browsed and downloaded.
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You need 1.3 GB free on one of your memory cards (this includes the built-in 2GB on the N810), although after installing, you will only need 1 GB.
You need to keep your expectations reasonable. Big desktop applications like OpenOffice and Firefox run slowly on the tablet. They are designed for big, power-hungry CPUs. The N8x0's processor is comparable to a Pentium II processor. Just imagine running these apps on your computer from the early-mid-90s (remember Windows 95?), and you'll get the idea. But sometimes, you really need something on the tablet that only these apps can provide, like MS Word compatibility or Java applets.