Reinstall Vista, Install Vista SP1 and
SP2 RC. Keep going back to Windows Update until there is no more fixes to update.
You can try to load ZA if you must have it. But ZA isn't really needed. Use the Windows Firewall and a good router you'll be plenty safe,
I use AVG, Windows Defender and run Trend Housecalls once a week.
Forget Adaware. I'm dubious about SpyBot.
The best defense is not clicking on suspected sights and stop downloading clown midget porn.
If you use firefox, you can use AdBlock to keep stuff from loading on a page. Flashblock and NoScript go a long way to keep your computer safe
If you can find a version of Windows 7, try that. It's heads and tails above Vista and will solve most of your problems.
I've bene running Windows 7 for a few months. It's everything that Vista isn't. Stable, fast and easy to tailor to your needs.
ZM.