Temporary file from UsrClass.dat (sometime associated with NTUSER.dat)

UsrClass.dat{randomnumber}.TM.blf’s file filing up your user hard disk space ? It’s what and can we erase them is what I will talk today. (if you can’t run the diskcleanup wizard)

10-20-2016 12-16-40 PM.png

(or/and with those files)

10-20-2016 12-21-20 PM.png

A background; those files are temporary registry settings that are not yet wrote in UsrClass.dat. The OS to prevent some corruption write those files in the registry when it determine it’s ok to write them safely. The file act like a .TMP’s file.

UsrClass.dat contain : HKEY_USERS\<User SID>_Classes (HKEY_CURRENT_USER\Software\Classes) (source)

If your profile is fulled with those files it mean something broke the OS’s step. It’s a warning to check what happened to fix the real problem. We start by checking the Event Viewer;

In my case I used one file timestamp to search correctly the eventlog.

10-20-2016 12-13-05 PM.png

I was able to find it was caused by a scheduled restart, and that a service was giving an error.

10-20-2016 12-14-30 PM.png


For me after analyzing the why and the file I can safely remove those files. A note, running the diskcleanup tool would had been a lot more safier and faster, but in my case I wasn’t able.


Thanks !


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