Logs, logs, logs - Location of Various Log Files on Windows

The location of various log files on Windows are in the local user's temp folder.

e.g. In most cases, the Windows Installer log files start with msi, end with a .log extension, and includes a group of characters. For example, the Windows Installer log will have a file name that resembles the following: msib3a6g.log.
These log files are located at %temp%, i.e.

• XP:
• C:\Documents and Settings\ {UserName} \Local Settings\Temp\
• Vista:
• C:\Users\{UserName\AppData\Local\Temp
• Windows 7:
• C:\Users\{UserName\AppData\Local\Temp

 

See this link for turning on full verbose logging for Windows Installer:

http://support.microsoft.com/kb/958052