why an extra file for portable use?
thats not very elegant and pretty annoying to have too much files in my portable exe folder.
exe+ini should be enough..
have you tried deleting that .DAT file and seeing if CC still runs?
if it doesn't, there's your answer why it's there.
if it does, maybe there is no need for it.
The portable dat file tells ccleaner not to be able to activate certain features (such as context menu additions, and forcing settings to ini). It's empty and you can delete it but I think it's pretty useful and takes no space (it's a blank text file with dat extention)