The files would be in Windows \ Logs.
There are several fix options for the Web Installer issue -
-Your UAC settings may be too high. You could try disabling that.
-Even if you are logged in as Administrator you can R/click on the Web Installer
dxwebsetup.exe and go to Properties \ compatibility and tick 'run...as an administrator'.
-Boot into Safe Mode and run the Web Installer from there.
d3dx9_43.dll may be installed, but may be corrupt.
Go to Windows \ System32 and SysWOW64. If the file is there and you are still having an issue with World of Tanks then delete the file from each folder and run the Web Installer . The Web Installer will replace the 'missing' files.
If the issue persists after installing a new copy of d3dx9_43.dll then make a copy and place it in the games main install folder.
failing all the above you may want to try running System File Checker -
SFC /SCANNOW Command - System File Checker - Windows 7 Forums
In cases where there is a DirectX error and no specific file is named it is better
to run the DirectX Redistributable installer. This is the full Direct X package and
this installer will overwrite the existing files. The Web Installer does not overwrite
existing files.
Download Details - Microsoft Download Center - DirectX Redist (June 2010)
.