That all depends on what you intend to use the pc for?
I'm presuming you're not gonna be using this for gigs? This is simply your home PC right?
Norton/Symantec &
McAfee are the recognised leaders for virus protection and are both very similar in my experience.
You may wanna get software for ripping CD's such as
MusicMatch,
Cdex etc. I know that Nero is able to rip, but IMO it's not easy to use.
You may wanna get music database software such as
CATraxx for cataloguing your vinyl, cd & mp3 collection.
You may need
SpyBot. This will remove from your pc any spyware which is loaded without your knowledge while surfing the net.
What else you'll need depends on your needs?