I think that I can help you out. However, you will find that computer security usually isn't that quite simple. There are a few common mistakes that the typical computer user makes.
First and foremost, if you're utilizing a Windows XP operating system ensure that it has Service Pack 2 installed. Additionally, you should have the "Automatic Updates" feature turned on so that it both downloads and installs security updates without user intervention. Set the installation time to an hour that the computer is usually on.
Next, you should set up separate profiles (a.k.a. login ID & password) for administrator activities versus everyday use. You should avoid surfing the Internet using an account with admin privileges whenever possible. Maintain your day-to-day account at the "User" (also known as "Limited User") level. This will go a long way towards avoiding problems with spyware & malware in particular.
As far as a "do it all" program, the industry leader right now is Symantec/Norton AntiVirus. Their latest versions do a good job of protecting against both viruses and spyware. As a potential alternative, there is AVG Anti-Virus free edition...
http://www.grisoft.com/doc/40/lng/ww
Even if you do choose one of those products, you should probably still keep at least one spyware program readily available. Ad-Aware is the most popular, and even if you only run a scan once a month, you're still being proactive...
http://www.download.com/Ad-Aware-SE-Personal-Edition/3405-8022-5153545.html?part=dl-ad-aware&subj=dl&tag=top5
As one more additional step, you should consider using a secure "hosts" file. It will protect you from numerous spyware threats, in addition to eliminating virtually every popup you can imagine. Again, updating this at least once a month will help protect your system significantly...
http://www.mvps.org/winhelp2002/hosts.htm
Finally, if your computer really has that may virus and/or spyware problems at the moment, you should seriously consider backing up your important data, wiping the hard drive, and performing a clean install of WinXP. Combined with the steps I described above, your "new" machine should be much better protected from any potential threats...
http://windowsxp.mvps.org/XPClean.htm
Sorry...that was a bit long-winded, but hopefully beneficial!