Goodmorning everyone.
I just upgraded to the IDE 1.6.5 and with surprise, compiling the sw that worked with the previous version, I get this error message:
Can not run program "{runtime.tools.avr-gcc.path} \ bin \ avr-g ++" (in directory "."): CreateProcess error = 2, can not find the file specified.
What do I have to change to make the compiler?
SO : Windows 7 home 64 bit
Thank you very much for helping 
You can try uninstalling the IDE and do a reinstall.
From which version did you upgrade?
Before you re-install you may want to delete the Arduino15 folder.
A bunch of people have had IDE 1.6.x problems, including IDE crashes and bizarre compile errors, when they have an old 1.5.x/1.6.x installation. Those problems seem to be caused by out-of-date executables that the new IDE saves outside the IDE installation directory. In such cases it appears that the fix is to delete or rename the old "Arduino15" directory and re-install 1.6.x.
On Mac OS X:
/Users/(username)/Library/Arduino15
On Windows:
C:\Users(username)\AppData\Roaming\Arduino15
On Linux:
/home/(username)/.arduino15 (a.k.a. ~/.arduino15)
I changed the name of C:\Users(username)\AppData\Roaming\Arduino15 and everything is working good.
Thanks for help.
Best regards
Thanks for all the help guys really appreciate it!
Problem solved when delete the old "Arduino15" directory and re-install 1.6.x.