Many for-pay antivirus programs, such as Symantec's Norton AntiVirus, are system hogs, taking up far too much RAM and system resources, which slows down your PC unnecessarily. Not only that, but you have to pay an annual fee for using them.
There's a better way: Get the Avast Antivirus software from ALWIL Software. It's lightweight and takes up barely any RAM or system resources, it's simple to use, and it'll do everything you need by providing live, resident protection as well as scanning.
The software uses a shield metaphor for its multiple types of protection. There's an antivirus shield, one that protects against Web-based threats, another for e-mail protection and so on. You can customize the sensitivity of each shield.
Avast includes automated updates of virus definitions. The independent testing site AV-comparatives.org rates its effectiveness as Advanced+, the top level. I've been using the program for well over a year and a half, and it's caught every threat that's come my way.
Note that Avast is free for home use, but requires payment for business use.
Everybody should be using spyware-detection tools such as Lavasoft Ad-Aware or Spybot Search & Destroy — preferably both. But some malware is so nasty that it escapes detection from any spyware scanners — and can't be removed by them, either.
So what can you do if your PC is acting strange and you suspect that you've been victimized by malware? Try downloading and using Trend Micro's HijackThis, and with the help of experts, you may be able to track down the source of the problem and then fix it.
The program examines your settings and the Windows registry, particularly those sections that are most likely to be vulnerable, and then saves all those settings in a log file. Those settings are the key to finding out if you've been infected. Experts can analyze the log, and from what they find, determine whether there's a spyware infection.
Where do you find the experts? The program lets you upload your log file to the HijackThis Web site, where others will examine it, let you know if there are any likely infections and tell you how to rid yourself of them. There are plenty of other discussion areas on the Internet that will do the same; a Google search will turn up plenty of them.
The software will also delete suspicious items, and it includes other useful tools, such as one that will generate a log of all programs that run on start-up. Keep in mind that if you're not an expert, you shouldn't try to use this program on your own. Think of it as a last resort when standard anti-malware tools fail.
Of course, the best way to protect yourself against spyware is to make sure that it doesn't install in the first place. That's where SpywareBlaster from Javacool Software comes in. It stops the installation of ActiveX-based spyware, browser hijackers and other malware, and can also block spyware cookies.
It includes extras as well, such as disabling Flash running in Internet Explorer. And it also lets you create a system snapshot, so that if at some later point you get infected with spyware, you can always revert to a clean system.
Note that if you don't use Internet Explorer, there's no need to install this software, because Firefox, Opera and Safari don't use ActiveX.