For security on my laptop I run NOD32.com and MalwareBytes. I was a bit disappointed that NOD32 missed some malware recently, that's why I have MalwareBytes too.
Office 2007 will run fine. It runs fine on my Acer One.
I recommend Spotify for free music. Also, make sure you have a backup solution in place, i.e. external USB hard drive.
Enjoy your new netbook!
Rgds