Antivirus, firewall and text-editor is the "base" software, which you will install probably firstly on the clean Windows.

I’m preferring this ones for the non-business (home) usage:

Comodo firewall (freeware for personal usage) - Comode is excellent firewall. It’s better, than for example famous Zone Alarm (in free edition absolutely).

Avast - Home edition (freeware for personal usage) - Avast scores every time in the Virus bulleting test , very good antivirus which consume only small part of the memory (not as the Norton Antivirus). If you looking for the antivirus for your business Eset NOD will be better solution (Avast sometimes indicate virus in the clean files).

Open Office (open-source rock ) or czech edition on http://www.openoffice.cz - OpenOffice Is excellent replacement for the "famous" Microsoft Office. Open Office is open-source you may use it for your business too!!! Whole my business accounting (include tax reports, many graphs, government reports…, stocks speculator diary ) is in this OpenOffice. Software is opened, it’s free and document standard is opened too (.ODT, .ODS ), so you may read it after 50 years without any problem…