Hello,
Are you uninstalling SEP and Liveupdate from the Machine?
Do you have any other Symantec Product on your machines?
Do you have SEPM installed on the same machines?
If the answer to the first is yes, for second is No and for Third is No, then you may surely delete these files.
Or else, I would recommend not to delete these files.
\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate\Downloads is the place where all the definitions gets downloaded.
\Documents and Settings\All Users\Application Data\Symantec\Cached Installs\ is the place where you would find the Product GUID.