"did you tried with the following option, This will drop the existing sample db and then create new sample db.
$ db2sampl -force
If this doesn't help then you need to delete db directory manually and the create SAMPLE db using…"
"Create sample database using db2sampl cmd. The will create a sample database for you and will create all the tables required by default
1) login as a instance owner and run the following command
$ db2sampl Creating database…"