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Use Registry Editor to add or to modify the following registry entry:
Value data: 10002 (Hexadecimal)
Note To disable logging, select NONE (0x00000000).
You can combine these values. For example, you can combine VERBOSE 0x00000002 and LOGFILE 0x00010000 to get 0x00010002. Therefore, if UserEnvDebugLevel is given a value of 0x00010002, LOGFILE and VERBOSE are both turned on. Combining these values is the same as using an OR statement.
The log file is written to the %Systemroot%\Debug\UserMode\Userenv.log file. If the Userenv.log file is larger than 300 KB, the file is renamed Userenv.bak, and a new Userenv.log file is created. This action occurs when a user logs on locally or by using Terminal Services, and the Winlogon process starts. However, because the size check only occurs when a user logs on, the Userenv.log file may grow beyond the 300 KB limit.
Although the 300-KB limit cannot be modified, you can set the read-only attribute on the Userenv.bak file, and the Userenv.log file will grow indefinitely. You must only use this method temporarily, remove the read-only attribute on the Userenv.bak file as soon as you are finished troubleshooting.