Antivirus software: Revisiting the ridding of the Norton

I've read old posts here about Avast, AVG and other antivirus software. This laptop came with Norton installed. The initial Norton subscription has lapsed and I'm not renewing it because I've already thrown enough cash away on past failed Norton Updates that never installed successfully on another computer. I vote with my feet and am happy to walk away from Norton.

My quest for help is two-fold:
1) Quick input on what anti-virus software people have tried that has gained their approval. I'm willing to pay for a good product, or Free works for me, just as well.

2) When I decide on an anti-virus program or whatever you call it; how do I go about removing Norton, installing the new, and in what order? Remove old first, install new second? Does it matter? I'd be really grateful if the process were close to idiot-proof.

I have Windows Vista Home Premium with Service Pack 1 on an HP Pavillion laptop and DG as my homepage, it goes without saying....

Thanks for any leads and tips you can offer.
Poochella