the slave drive in the new computer is the 'C' drive that came out of your old one?
Provided you have no programs installed on that drive , and provided your operating system is installed on the new drive you can safely delete the old .cab files, BUT.............
To be on the safe side do this:-
Create a folder on the slave drive - call it old_cab.
Then drag all the old .cab files into it and use the computer for a while. Once you're happy that things are running OK you can go back and delete the redundant files.