In the first week after the release of Microsoft Security Essentials, Microsoft says, the software was downloaded 1.5 million times. The software detected nearly four million security problems on 535,752 different PCs.
According to the company, there were far more problems detected on Windows XP machines than on Vista or Windows 7. You can see the results below.
Microsoft said this is in keeping with the general trend that less malware is found on newer operating systems and service packs.
Some of the more interesting findings come from an analysis of threats by country. In the U.S. Trojans are the most-common malware, while in Brazil it's worms, notably Conficker and Taterf.
For more information, check out the findings from the Microsoft Malware Protection Center.