The best tools I've found are:
1. WebRoot SpySweeper. If you want to pay, this is what to get. This tool is quite excellent.
2. Autoruns. This is free from Microsoft and can be downloaded at
www.sysinternals.com. This is good if you know what you're doing, is free, and is very effective at removing "Browser Helper Objects".
3. Rootkit Revealer. Another free one from Microsoft, also available at
www.sysinternals.com. This is a good tool for removing rootkits.
4. AVG Grisoft Anti-Rootkit. This is available at
www.grisoft.com, and is also incredible at what it does.
5. Spybot Search & Destroy. This is still an excellent tool to have, and is constantly getting updated.
6. Spyware Doctor. Part of Google Pack, and also has a Pay version. Still a very good tool.
7. Trend Micro's Antivirus program. Their program consistently beats the free ones, Symantec, and McAfee. It also happens to be less of a system hog than any of them (AVG being the worst hog of them all!).
8. Kerio Personal Firewall. Yes, it's that good. This is a firewall that is significantly better than ZoneAlarm, the Windows Firewall, or the Symantec product.
9. The Ultimate Boot CD For Windows (
www.ubcd4win.com) version 3.04. This has all the tools you need on one convenient CD, and boots into an alternate version of Windows. This is good because you can scan for rootkits/spyware/adware/viruses without booting into Windows, and remove the tough ones with no issues.
Also, if you manage Windows Servers, this comes with drivers for the HP Proliant RAID controllers, so you can use this to rescue data from dead servers.
10. Ad-Aware SE. This is still one of the best anti-spyware products out there.
11. Opera. This is hands-down the most stable browser on the market, and is also the fastest.
12. Firefox. This is also a great browser, and has a large amount of anti-adware and anti-spyware plugins available for it.
The programs I'd avoid are:
1. McAfee. This is a performance killer and is not that effective. I mean this across the board with all of their products.
2. Norton Internet Security. Symantec makes decent Antivirus, and that's it. Don't spend the extra bucks for the personal firewall that kills your system performance.
3. ClamAV. Not as effective as Trend, and a performance killer.
4. AVG Free Edition. For a free product, it's good. I would not pay for it. This also kills disk performance and your speed when opening Word or Excel documents.
5. RegClean. This was designed for Windows 95. It will cause damage if you use it on an XP system.
6. Internet Explorer (except for Microsoft Update). IE7 didn't fix that much unless you run it on Vista.
I've been in the business over 10 years, and am currently doing system architecture work for my customers. I still keep my skills in desktop support so that I know what goes on from the whole enterprise perspective with them, especially when it comes to how systems can get messed up.