Microsoft has released some first-week usage statistics of its new antivirus application, Microsoft Security Essentials (MSE). Redmond made the program available to users in 19 countries on September 29, and it accumulated 1.5 million downloads in the first seven days – though, it's unknown how many individual systems are actually running the product. That said, Microsoft does know how many computers are infected.

The software giant says that during the first week in circulation, MSE detected malicious software on precisely 535,752 machines – and the actual malware count is eight times more than that. Microsoft says early adopters of Windows 7 seem to be the most prominent users of MSE, which seems logical enough, and around one third of those systems are running a 64-bit version of Windows 7.

The general consensus seems to be that MSE is a relatively solid product, and with some 4 million malware detections in its first week, Microsoft's antivirus is at the very least helping some users to keep clean.