Windows: free antivirus from Microsoft
Microsoft offers a FREE antivirus/anti-other-bad-stuff application called “Miscrosoft Security Essentials”.
It is NOT the best thing out there, but works pretty doggone well. It DOES “suck up some CPU cycles” – i.e. when it’s running your machine will slow down a bit.
It is DEFINITELY better than running nothing – so if your subscription to Norton or Symantec or whatever is running out, and you don’t have the cash, check it out.
http://ct.techrepublic.com.com/clicks?t=523334930-a275dfeedae0baeeab728d8c7a14c0c1-bf&brand=TECHREPUBLIC&s=5
for an article about it, with links to the download.
More details at
http://blogs.techrepublic.com.com/products/?p=839
Download the product at
http://www.microsoft.com/security_essentials/default.aspx
I am using using it on one of my machines, and it seems to work well. When it’s scanning the machine does slow down, but this is on a slower Pentium 4 machine.