After doing patch-Tuesday update yesterday, my Windows 7 no longer booted. This is the second time it happened. Last time I fixed it, didn’t get to document and it took me a while to figure out how I did it.

This version of Windows is Windows 7 Professional 32-bit. After some digging, MpFilter.sys is Microsoft Malware Protection Minifilter, which is a part of Microsoft Security Essentials (MSE). MSE is installed on my Windows 7 machine.

The fix is to boot from Windows 7 DVD, selecting “Repair your computers”. Then click on the command prompt option.

After that, just reboot the machine. It should work. Finally, uninstall and reinstall Microsoft Security Essentials (or use a different antivirus program).