Ask HN: What are your tricks for fighting malware?

For the first time in maybe 10 years I got a bad download yesterday that just about destroyed one of my Windows computers-- registry edits have stopped me accessing the internet from it (proxy settings overridden and greyed out in internet settings) and background scripts I can't find are continually downloading and running adware at such a pace that the computer is too exhausted for me to even open the control panel before the screen fills with other windows.

As a software engineer, this was frustrating. What have you done when things like this happened to you, besides reformat?