Okay big guy, here we go.
First of all. Media Players
Most internet sites use Windows Media Player (version 9 is the best, you can have a little window on the task bar so when you play a DVD, you can just have it there on top of everything and it won't get in the way much and if it does, minimize it and listen to it, also has basic buttons on it) or Real Player, so basically, get both. I still use WinDVD 5 for my DVD's as functionality works great on it (and time stretching is fun, try it on the Yoda Fight sequence in AOTC and you'll see why)
And I personally think the best freeware antivirus software out there (and my school uses this and has been virus free since
1997 4 days ago when I threw in my trojan horse Mwuahahahaha!) AVG Antivirus software.
Hope this helps.