How do you keep your computer secure?

Here's how Robert Scoble of Microsoft does it.  From his post and with my comments:

1. Install Windows XP SP2.  I personally haven't had any compatibility problems; of course I haven't yet upgraded at work.  The security is very much increased in SP2.
2. Get a good anti-virus program.  You can still read my earlier post about getting 12 months free of Computer Associates EZ Armor Virus protection and Firewall.
3. Get a good two-way firewall on every machine. See above for the link to EZ Armor or go to some of Socble's free recommendation of the Sygate Personal Firewall or pay for Zone Alarm.
4. Get a hardware-based firewall or NAT at point of network entry.  You can get this on a very cheap Linksys router for your house or business.
5. Turn on automatic updating.  If you follow the first tip, SP2 tries to do this for you at every turn.
6. Run the latest email and Web clients.  New clients traditionally have the best updates and most security.  Run Firefox as your web browser; not only is it secure, it's got great features.
7. Visit www.microsoft.com/security regularly.  It's the official Microsoft site for security, but chances are that you will get a lot of what you need via Windows Update.
8.  Run at least one good anti-spyware program like Adaware or Webroot's Spy Sweeper or Spyware Blaster.  I like Spybot Search and Destroy and Adaware myself.
9. If you visit high-risk Websites, turn off ActiveX and scripting in your browser.  This includes turning off scripting in Firefox.
10. Don't run in administrator mode.  This is super-hard to do; I tell everyone else to do this, but can't seem to get there myself.  If you are a casual user, don't need to install software or tinker with things, consider using a Power User account on a day-to-day basis.
11.  Keep an install partition on each of your machines.  Hard drives these days are big enough to accommodate this without a problem.  Even better is to image your main drive to an external drive so that you have a snapshot in time that you can back-up in minutes.  The best software for this, hands down, is Norton Ghost.
12. Use better passwords.  Stop using your birthday or your last name or silly words that are easy to crack.  Random numbers and letters and random capitalization will make it hard to guess your password; I use something to that effect and it is surprisingly easy to memorize.
13.  Backup your data regularly.  If you are not going to image your whole drive, consider buying an external drive and using offline files so that every time you disconnect from that external drive, you get a copy on your computer and a copy on your external drive.  Even better, run a weekly back-up program.

You can never be secure enough and most of the items above require little to no investment.  If you need to buy hardware such as routers and hard drives, keep your eye on your Sunday paper for sales and mail-in rebates.  For software, peruse Amazon and look for mail-in rebates; sometimes you can get good software for free after mail-in.