Since Win 7, (or VISTA) *.chm files are no longer being used for help files. You have to download the old chm program files from Microsoft if you need to use a Help file made in the old chm format.
Current help files are html documents for offline viewing.
The SONAR Reference Guide (don't know where that is yet as I'm still downloading part 2 of the SONAR X2 installer) is usually a pdf and has the same content as the help file but not context sensitive ie not accessible from within the different parts of SONAR.
Wish I knew where that file was?
I've extracted Parts 1, 3 & 4 of the installer and so far have
02_SONAR_X2_Producer.part1:
Setup-1.bin,
Setup-2.bin,
Setup-3.bin,
Setup-4.bin,
02_SONAR_X2_Producer.part2
Setup-5.bin,
Setup-6.bin,
Setup-7.bin,
02_SONAR_X2_Producer.part3:
Setup-8.bin
Content\Perfect Space
Content\RXP
02_SONAR_X2_Producer.part4
Setup.exe,
Setup-9.bin,
Setup-10.bin,
that's it for the SONAR files