Here is how I dealt with viruses and worms until March 2005.

This is sure to be almost nobody's favorite way to scan a hard disk for viruses in Windows XP...  I use F-Prot Antivirus for DOS after booting from a floppy.  It's the only way I can make F-Prot scan the whole c: drive.  Otherwise it scans a few folders and quits, whether XP is in Normal or Safe Mode.  I can make F-Prot scan a custom downloads folder whenever I decide to download some new file/program or other.  Matter of fact, you could point F-Prot at any directory of files and it will probably scan them all, even while XP is running... But again, it won't do the whole drive unless XP is out of the picture.  Beyond that, I can't really complain about the software.  Hey it's free. :)  You have to run and update it manually, and there's no installation as such... you make a folder and unzip all the files there.  When there are updates <--(scroll to the bottom of their page for the latest definitions), you unzip the files into the same folder, overwriting the older ones.  To start the program, you type its executable name (f-prot.exe or just f-prot) and a few command line switches.  F-Prot is one reason I'm still using the FAT32 file system, else I can forget about logging on to the hard drive from a DOS boot floppy... unless I decide to try my luck with a DOS NTFS boot disk.Occasionally, when I feel the need for a second opinion, I'll pay a visit to Trend Micro's Housecall, where a free virus scan can be had.

Here's how I treat viruses and worms now-- AVG Free Edition.  It slows the machine a bit but it works well and it gives me the second opinion I'm after, especially when it comes to email.  F-Prot for DOS got to be a real problem after I went from FAT32 to NTFS.  I still want to switch back to FAT32 (I'm waiting for my next big Windows XP screw-up to give me an excuse to reinstall) but I'm in no mood to use a DOS based antivirus program anymore.

And then sometimes (like as of this writing) I get sick of AVG's heavy hand on my system.  Times like this, I either pull a few of AVG's claws out, or dump it and use McAfee AVERT Stinger for a while.  This one apparently only gets updated when a major new virus turns up, still can be handy though.  It's almost a standalone utility, only seems to require one support file to work.  I first noticed it in the freeware section at Windows Support Center.  Note that I NO NOT recommend using AVERT Stinger all by itself, except to crazy people who like to drive one-handed with their head out the window!

There are other free antivirus alternatives like, Avast! Home Edition, PandaActiveScan, BitDefender, and AntiVir.

Like an antivirus app, nobody should be without a firewall, whether it's software or hardware or a mix.  Zone Alarm over here.   A Google search will turn up other free firewalls.  Sygate and Kerio are two others I've tried, but I'm a creature of old habits, and Zone Alarm does well enough.  Windows XP has a built-in firewall but the pre SP2 version only blocks incoming candy-grams, not the outgoing ones-- and the new Windows Firewall in SP2 isn't much better; should some kind of malware get onto your computer and try to use your Internet connection to make outbound mischief, Windows Firewall won't even bring up a warning message or dialog, much less stop it from getting out.

Ad Aware, Spybot S&D and Microsoft Windows AntiSpyware are many people's favorite scumware removers.  So is HijackThis!, a tool for ridding Windows and Internet Explorer of scumware that will hop a ride on Windows and IE's coattails without asking.

Also go to SpywareInfo for a wealth of tools and know-how on... you know.

At MVPs.org, there is an area called Dealing with Unwanted Spyware and Parasites.

PC Pitstop has online diagnostics for Windows PCs, things like a disk scan, a video performance test, Internet connection test, ActiveX check, and more.  Internet Explorer is the preferred browser for using PC Pitstop, though not an absolute must.  See this page for details about a plug-in for Mozilla and Opera.

Microsoft has some good information on keeping XP and other OSes secure.  This one's called the Microsoft Protect Your PC Web site.

Steve Gibson's Shields Up! is a good place to test your Windows security.  I pop over there and here to satisfy myself that the firewall is working correctly, and that certain Windows 'features' are turned off.  But these are only part of what Gibson's site has to offer.  See for yourself.

You could surf the Web for days and have security/privacy pages coming out your eye sockets.  Eric Howes' Privacy & Security Page is one of the better ones I've bumped into.  So is this one called Safety on the Internet, aimed mainly at beginners, still a good place to visit.