Why is this MSS.log file locked? Is your backup program stumbling over it? Maybe you get this error:
The process cannot access the file because it is being
used by another process.
MSS.log is used by Microsoft Search. MSS probably stands for Microsoft Search Service. To unlock the file, go to Control Panel > Administrative Tools > Services and then look for the Windows Search service; click on it, and click Stop in the left. Now the MSS.log file should be unlocked.
But, Windows Search is the program that allows you to search from your start menu and other places in Windows, so I don’t recommend stopping it. If for some reason a backup program is having trouble with it, consider telling the program to exclude that directory; if your backup program can’t do that, find a better program.
I only found this out because I’m having problems with Windows Search and trying to figure out how to read MSS.log… But upon Googling, I noticed that most people are having trouble with the file being locked. So, hopefully I helped you, random Googler! Good luck on your quest for backups; meanwhile I’ll keep looking around for why my Windows Search service keeps crashing and restarting, using 100% CPU time…
Oh, and if you even came here because your Windows Search is broken, read these answers: http://superuser.com/questions/101431/windows-7-search-indexing-is-stuck