quick guide >
if you download this
http://www.winmd5.com/ unzip it / run it and use it to check your downloaded files.
in that program,
first "browse" bit is the file you want to check..
e.g.
c:\Downloads\02_SONAR_X2_Producer.part1.exe
and you'd copy / paste the code below the file into the "original file checksum" e.g.
f7406ba9af35a75b03b91dc464aec3dd
(that is what the downloaded file SHOULD be = to) and it will be calculating what your file checksum is compared. they should (hopefully) be the same
arachnaut and Ryan from Cakewalk provided a list earlier
EDIT: Updated checksums and file sizes here:
http://www.cakewalk.com/x2install