Windows Updates are failing on one of my users' computer. Update returns "Code 606 Windows Update encountered an unknown error." I enabled verbose logging per http://support.microsoft.com/kb/958052 . Initially, I couldn't find the logs. They are supposed to appear in C:\Documents and Settings\ {UserName} \Local Settings\Temp\. Instead, they appeared in C:\Windows\Temp. I checked, and %temp% resolves to C:\Documents and Settings\ {UserName} \Local Settings\Temp\. Inside the log file, I found "Error 1606.Could not access network location %APPDATA%\." %APPDATA% resolves to C:\Users\ {UserName} \AppData\Roaming. I searched for the error, and followed the instructions in http://support.microsoft.com/kb/886549. I wound up changing several values in HKLM\Software\Microsoft\Windows\Explorer\User Shell Folders. I found it notable that there is also a key with the name "{3D644C9B-1FB8-4f30-9B45-F670235F79C0}." I'm still getting the same error. User is running Windows Vista Business x64 SP2. Here is a snippet from the most recent log file: MSI (s) (30:DC) [13:51:00:009]: Note: 1: 1314 2: %APPDATA%\ MSI (s) (30:DC) [13:51:00:009]: Note: 1: 1606 2: %APPDATA%\ Action start 13:50:35: CostFinalize. MSI (s) (30:DC) [13:51:00:009]: Product: Microsoft Office Professional 2007 -- Error 1606.Could not access network location %APPDATA%\. MSI (s) (30:DC) [13:51:00:009]: Note: 1: 1606 2: %APPDATA%\ MSI (c) (AC:9C) [13:51:00:009]: Creating MSIHANDLE (154) of type 790531 for thread 3228 MSI (c) (AC:9C) [13:51:00:009]: Creating MSIHANDLE (155) of type 790531 for thread 3228 MSI (c) (AC:9C) [13:51:00:009]: Closing MSIHANDLE (154) of type 790531 for thread 3228 Error 1606.Could not access network location %APPDATA%\. MSI (s) (30:DC) [13:51:00:009]: Product: Microsoft Office Professional 2007 -- Error 1606.Could not access network location %APPDATA%\. MSI (c) (AC:9C) [13:51:00:009]: Creating MSIHANDLE (156) of type 790531 for thread 3228 MSI (c) (AC:9C) [13:51:00:009]: Creating MSIHANDLE (157) of type 790531 for thread 3228 MSI (c) (AC:9C) [13:51:00:009]: Closing MSIHANDLE (156) of type 790531 for thread 3228 Error 1606.Could not access network location %APPDATA%\. MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Note: 1: 2262 2: InstallExecuteSequence 3: -2147287038 MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Note: 1: 2262 2: InstallExecuteSequence 3: -2147287038 MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Note: 1: 2262 2: InstallExecuteSequence 3: -2147287038 MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Note: 1: 2262 2: InstallExecuteSequence 3: -2147287038 MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Transforming table InstallExecuteSequence. MSI (s) (30:DC) [13:51:00:009]: Note: 1: 2262 2: InstallExecuteSequence 3: -2147287038 Action ended 13:51:00: CostFinalize. Return value 3. Action ended 13:51:00: INSTALL. Return value 3.