My Windows 10 computer has been infected with TrojanDownloader:JS/Nemucod. This is a particularly nasty infection that quickly downloads and installs other programs. Windows Defender - the anti-virus/anti-malware utility I'm using that is included with Windows 10 - is finding and attempting to deal with the infections, and it seems able to remove them temporarily... ...until I open a particular message folder in Thunderbird, after which I'm quickly alerted that the infections are back. I'm also alerted that they're back after I open Settings in Thunderbird for the email account associated with the folder. There's a message in the folder - the most recent one - that I strongly suspect is the source of the problem. I'd like to delete the message and see if that helps, but Thunderbird crashes each time I left-click the message to select it and then either right-click and select Delete Message from the context menu or press the Delete key on the keyboard. I've tried this with the Message pane both open and closed (I pressed F8 to close it), but the result is the same. I've also tried deleting Trash folders in case they were corrupted, as described on https://support.mozilla.org/en-US/kb/cannot-delete-messages , but that didn't help. From what I've read in the support forums, such as https://support.mozilla.org/en-US/questions/1210862 , I don't understand how I got the infection in the first place. I'm always careful with suspect emails, and I'm reasonably sure I didn't open the suspect message. Have any of you dealt with anything like this? Thanks! Mitchell