There is always a ritual that is carried out on a new (or even old PC), which involves removing as much pre-installed software as possible and then replacing it with useable and essential alternatives.
(I am certain I have done a similar post like this before...)
Here is my install ritual:
(Please note that all the software listed on this page is both legal and free. No pirate programs in this list. Many will also be opensource.)
Firefox. Many prefer Chrome, but I prefer Firefox (en-gb localisation). I like how it works and I don't think google monitors it as actively as chrome. Another alternative is Opera Browser.
Whatever is chosen, the idea is to get off Internet Explorer as quick as possible.
For a while now I have been sing Microsoft's Security essentials which is free and without hassle on all PC's with legitimate windows Installs. Unlike some other alternatives, its licensing doesn't have a "free for home use only" clause.
Coverage wise, when I started using it, it used to be very good, but I don't know if it has kept its quality or fallen down the rankings over time.
Other alternatives are Avast! (which last time I used it used to talk to me...) Avira Free, and AVG Free which I have used in the past. Comodo is another option which seems to have decent reviews, but I have not used.
I have heard good things about Malwarebytes, but ive not used it enough to really give it a rating. But I install it when I am setting up others computers. For myself I trust to not get malware, which is a bit arrogant and the best way to get caught out.
I use VLC which can play almost anything you can throw at it.
Many people use winzip. Here's a tip: don't.
7-zip is so much more featureful, and its actually legally free and without any restrictions. or nagging to purchase the "pro" version (because this IS the pro version!)
For vector drawing (like illustrator), there is Inkscape.
Word Processing / Office
I use LibreOffice. There is also Apache Open Office. Both are very similar, but I expect the former to be slightly more polished, though both are in urgent need of a makeover to look like they belong in this century.
Other Tools and Utilities
Notepad++ is a good addition for a notepad like application. Great for writing code.
WinScp for FTP/sFTP
IsoRecorder - Adds the feature to Windows to burn "iso" disc images.
Flash Player. To Play Flash on the web.
I think this covers most of the programs that are needed to set up a new windows install into something that is useful. If I have missed anything, or have better alternatives, please let me know.