Hi there.
The required software for a new PC to be "functionally literate" are:
iTunes/Quicktime @
www.apple.com FreeWare, but you shouldn't use it as your main player, aspecially with MP3/4 players it erases music files it thinks you didn't pay for, it used to do that i don't have an mp3/4 player to check with every version, usefull to play ".mov" and other apple format files, other players use it's codec's.
Real Player @
www.real.com FreeWare the original internet streaming audio and video player, still as good as ever and it'd codecs are also used by other players.
DivX @
www.divx.com FreeWare one of the most used video format for long videos like hollywood movies, and the codecs are also used by other players.
Winamp @
www.winamp.com (optionnal) one of the best players IMO, the playlist system is the one i like the most.
Java @
www.java.com FreeWare used by many if not most internet based programs, also used for internet games.
WinZip @
www.winzip.com used to be FreeWare but it still is almost, used to create, compress and decompress .zip and .rar files, there are others but this is the most popular.
Avast anti-virus @
www.avast.com one of the best, and the best i have tested, but haven't tested them all, the virus database is updated almost daily, 6 months free pay after, but it is one of the best, worth the price, also protects against spyware.
Adobe Flash player @
www.adobe.com FreeWare, for internet explorer to display flash animations.
Adobe (acrobat) Reader @
www.adobe.com FreeWare, used to read ".pdf" files, which most technical documents and e-books are.
Silverlight @
www.microsoft.com FreeWare, in the sence that if you have windows you already paid for it, allows you to see silverlight animations.
Messengers, (optionnal) they allow you to chat with other users, there are several, most common are windows messenger @
www.microsoft.com and/or Yahoo messenger @
www.Yahoo.com both do the same thing roughly the same way and are FreeWare.
Burning software & DVD player, those are manditory if you have a DVD drive and/or recorder, you should use the one that came with your recorder, but if you bought your cpu second hand, or store assembled, you might not have the cd, but the software SHOULD be installed, otherwize you will have to buy it, WinDVD was the best DVD player until Correl bought it, now it's ok at best, burning software for most uses i like NERO @
www.nero.com and ez cd/dvd creator, nero is more down to business, while ez is easyer to use.
JohnDowe.