BitDefender: Trojan Disguised as Windows 7 'Compatibility Checker'
According to an IDG News Service article in The New York Times, the scammers steal their marketing text directly from Microsoft:
Find out if your PC can run Windows 7. This software scans your PC for potential issues with your hardware, devices and installed programs, and recommends what to do before you upgrade.
Users who install the attached file end up with a back-door Trojan horse program that allows criminals to do pretty much do whatever they want on the PC, like installing a keylogger to steal banking credentials or even gaining full access to the hacked system.