Error MSB6006: “mt.exe” exited with code 31

Question

I ran into this problem today while migrating a VS2008 solution to VS2010. The problem occurred in either of the following scenarios:

1. Rebuild Solution

Answer 1

Try turning off Windows Defender (or possibly other anti-virus related software). Windows Defender is known to lock files because MT.EXE runs after the linker is finished. WD jumps in the middle to check up on the newly built EXE and locks it up for the MT.EXE.