Not all software costs an arm and a leg. There’s lots of open source software out there which is available free (and completle legally) out there. Open Source is software in which the source code (the instructions that make it work) is freely available to anybody. They can then modify it anyway they like to suit what they need.
You don’t need to know anything about code to use it, you can just download and install it.

Open Office. This is sponsored by Sun and is a full office suite, word processing, spread sheets, databases and presentatioon software. It will open and save files in it’s own format and also in Microsoft Office format. You can download Open Office here.

Mozilla Firefox. This is a browser, like Microsoft’s Internet Explorer or Google’s Chrome. You can download Firefox here.

Mozilla Thunderbird. An email client from Mozilla, this works well for handling all your email. You can download Thunderbird here.

There’s also non open source software that’s available for free use in certain conditions. AVG provides a free version of their anti virus software for home use. It’s really good and anti virus is essential to protect your computer. Download AVG free here.