Here's a list of some useful software for Windows.
AbiWord is a slimline yet powerful word processor that I've used in the past. It can open files from Microsoft Word and OpenOffice.org, meaning you can open files that most other people send you. Did I mention that its free? :) We just got a new eight-year-old laptop (quite slow, little memory) and we're going to use this over the other options.
Irfanview is a simple image, sound and movie file viewer. Its free for personal use but you need to pay for it for commercial use. Anyway, it can view just about any picture under the sun, and then some.
Firefox is the best web browser for your computer. Forget Internet Explorer, pop-ups and the security problems that come with them, this web browser is simple, fast and a smaller download than anything I've seen before.
That's all for now folks