You are welcome to use your own judgement about these things but I present the information to let everyone know that it's there. For anyone on a budget it probably makes sense to give it a try.
Selections from the article;
For several years, two Czech software developers have offered free versions of their anti-virus programs to home users. These no-charge downloads don't offer every feature provided by McAfee Inc. and Symantec Corp., the two security developers whose programs come pre-installed on most Windows PCs. But when put to the same tests as software from the Big Two, they did the job almost as well and with less fuss.
Both of these freebies -- Avast 4 Home Edition, from Prague's Alwil Software, and AVG Free Edition, from Brno-based Grisoft Inc. -- can be installed only on home computers that aren't put to any business or commercial use. (Income from sales to businesses and organizations covers the cost of this exercise in Internet charity.)
These two programs share a few welcome traits. Both are relatively small downloads -- almost 10 megabytes for Avast, just under 15 for AVG -- that tout compatibility with systems as old as Windows 95. And both automatically download updates every day and allow quick manual updates.
AVG's interface is in general far cleaner than Avast's, putting all the relevant controls and status indicators in one window.
Neither program's screening was quite as far-reaching as that offered by competitors -- for example, Avast and AVG allowed me to preview a .zip archive containing a virus using Windows XP's Compressed Files tool, while Symantec and McAfee's software denied all access to that .zip file.
Also, neither Avast nor AVG will stop spyware that you choose to download and install on your own -- each pronounced a freebie, spyware-riddled download as safe. So you'll still need a separate anti-spyware utility such as Microsoft's free Anti-Spyware for Windows 2000 and XP.
But if you define an anti-virus utility's job as ensuring that no virus sent your way can run on your computer (as opposed to also ensuring that no virus can even land on your computer), these two programs were just as capable as their pricier competitors. And while I've gotten more reader reports than I can count of PCs immobilized by malfunctioning Symantec and McAfee software, I've yet to hear of such trouble with Avast or AVG.
Whichever virus scanner you use, make sure you keep one other active -- the one that came pre-installed at birth: your brain.
Even the most rigorously updated security software can miss a just-created program that hasn't been entered into virus databases, but any reasonably aware human should still be able to spot a con job when it arrives.
Be as skeptical and smart about strange files as you would any other strange solicitation, and you won't have to rely on somebody else's software as your only line of defense.
The urls are AVG and Avast.