my hp laptop got some viruses and i took it to bestbuy to get fixed but the guy replaced my norton and some other thing with hijack this and antivir which are worst than the others so now i need some better security to get rid of the trojans and stuff and keep them away

This is a HP laptop that my son uses and I want to know if this is something critical.

So I have a HP laptop that came with windows vista, Last week I got the bluescreen and it wouldnt boot so I took it to a computer store, backed up my data and downgraded to windows Xp. Now it works but my sound and video drivers doesnt and I’ve tried all my best but still no solution. I found my recovery cd and now I’m planning to reinstall vista but I dont wanna pay another 90bucks to back up my data again which is only 9gb. Someone suggested I back it up on a DVD, how do I do that? will it work? where will I get the DVD from? what other backup options do I have? Please help!!

I have vista home premium on my hp laptop.
I wanted to know all i need to get to maintain my laptops security.
like what kind of unti virus, what kind of spy ware and other things.