There are some links to free programs at the top of the forum.

I have no financial interest in this book whatsoever, but I am reading it at present, and it is an excellent resource for users of all levels. General computer maintenance as well as internet security is covered.
Rootkits for Dummies (Paperback)
by Larry Stevenson (Author), Nancy Altholz (Author)
It can be ordered from Amazon.com.

I'm sure all the info is available online, but having it at hand for reference is always a good thing.

Here are my tips, but most are also covered in the book in detail:

1. Visit Windows Update:
Make sure that you have all the Critical Updates recommended for your operating system and IE. The first defense against infection is a properly patched OS.
Windows Update: http://v4.windowsupdate.microsoft.com/en/default.asp

2. Adjust security settings for ActiveX:
Go to Internet Options/Security/Internet, press 'default level', then OK.
Now press "Custom Level."
In the ActiveX section, set the first two options ("Download signed and unsigned ActiveX controls) to 'prompt', and 'Initialize and Script ActiveX controls not marked as safe" to 'disable'.

3. Download and install the following free programs:
a. SpywareBlaster:
http://www.javacoolsoftware.com/spywareblaster.html
Tutorial here: http://www.bleepingcomputer.com/forums/tutorial49.html
b. SpywareGuard:
http://www.javacoolsoftware.com/spywareguard.html
Tutorial here: http://www.bleepingcomputer.com/tutorials/tutorial50.html
Periodically check for updates in both programs.

4. Please use a firewall and realtime anti-virus. Keep the anti-virus software and firewall software up to date.
Note: Zone Alarm Firewall (Zone Labs) http://www.zonelabs.com/store/content/company/products/trial_zaFamily/trial_zaFamily.jsp?lid=home_freedownloads
Sunbelt Kerio has a free version: http://www.kerio.com/kpf_download.html

5. You might consider installing Mozilla / Firefox.
http://www.mozilla.org/

6. Install spyware detection and removal programs:
You may also want to consider installing either or both of AdAware (free version) and Spybot S&D (freeware). Use these programs to regularly scan your system for and remove many forms of spyware/malware.

a. Ad-aware: http://www.lavasoft.de/software/adaware/

b. SpyBot S&D: http://safer-networking.org/en/news/2005-05-31.html

I would check for updates in SpyBot once a week or so.
Check for updates in Ad-aware frequently.

If you have recently installed AVG Anti-Spyware, it is a free trial product for 30 days. After that you can purchase it for full features OR you can also keep the free version to use as an on-demand scanner (recommended).
You will still be able to manually update it using the *update* button

7. Before using or purchasing any Spyware/Malware protection/removal program, always check the Rogue/Suspect Spyware List.
Here is the link:
http://www.spywarewarrior.com/rogue_anti-spyware.htm


8. Make sure you are using the most updated version of Java.
The current version is Java Runtime Environment (JRE)1.6.0
You can go here to download the latest version of Java Runtime Environment (JRE) 6.
Scroll down to where it says " The J2SE Runtime Environment (JRE) allows end-users to run Java applications".

Click the link to download the Windows (Offline Installation) package: Save it, do not run it. When the download is complete, close the browser.

Remove all prior versions using Add/Remove Programs, and delete the Java folder in Program Files.
Reboot your computer once all Java components are removed.
Then from your desktop double-click on jre-6-windows-i586.exe to install the newest version.
Official JAVA Installation Instructions if needed.
Reboot.

9. Practice Safe Surfing with with SiteAdvisor by McAfee. SiteAdvisor is a browser plugin that assigns a safety rating to domains listed in your search engine.
The following color codes are used by SiteAdvisor to indicate the safety of each site.

Red for Warning
Yellow for Use Caution
Green for Safe
Grey for Unknown


10. Here are some helpful articles:
"So how did I get infected in the first place?"
by TonyKlein
http://computercops.biz/postlite7736-.html

"I'm not pulling your leg, honest"
by Sandi Hardmeier
http://www.microsoft.com/windows/IE/community/columns/pulling.mspx

I hope this helps. :)