About.com's Tony Bradley takes PC Tools to task for their dubious claims...

Vendor Claims Vista Less Secure Than Windows 2000 - About.com

Based on the PC Tools Software results, one would expect to find 64% of all Vista PC's infected with some type of malware, however the data from Microsoft's Malicious Software Removal Tool for the second half of 2007 show that the number is actually less than 3% (compared with 5% for Windows 2000 SP4).
Though many of us have a soft spot for Windows 2000, nobody I know that runs Vista has yet to be infected by malware. You?