Trojan.Downloader.Mierwer.A. is a Trojan name that MalwareBell 3.2 uses as a fake warning message, alarming that users computer infected. with saying:

"Malware: (none)
mmviewer_emg11.cab Listed by SpywareBlaster as
Trojan.Downloader.Miewer.A."

Trojan.Downloader.Mierwer.A. message can come to users computer after Fake video codec like Video ActiveX Codec installation, but actually those codec’s are a Trojan zlob. The intention behind all the Trojan.Downloader.Mierwer.A. is to buy "full" version of Malware Bell 3.2 Rogue anti-spyware software or other spyware like Files secure, IE Defender. If user clicks on
Trojan.Downloader.Mierwer.A. fake warning message the browser will be redirected to website where user can buy Malware Bell 3.2 "full" version. But, Malware Bell 3.2 shouldn’t be trusted because it is a Rogue anti-spyware software. We recommend scanning your computer in order to eliminate Malware Bell 3.2 threat.