This time I have used the File Monitor... to track the file Read/Write
At one moment, after various access to the C:\WINDOWS\assembly\GAC_MSIL\System.Windows.Forms\2.0.0.0__b77a5c561934e089\System.Windows.Forms.dll
the system request the access to the file C:\WINDOWS\assembly\GAC_MSIL\System.Windows.Forms\2.0.0.0__b77a5c561934e089\System.Windows.Forms.pdb which is the symbol file of the above dll.