by John McGettrick.
Hi William,
It sounds like it was not removed correctly as Moodle seems to think that the database tables exist, you could verify this by checking the mdl_config_plugins file to see if there is an entry for plagiarism_turnitin. I think the best thing would be to uninstall the plagiarism plugin being sure to remove the turnitin folder from the plagiarism directory. Then you can try re-installing it as any reference to the plagiarism plugin should have been removed.
If this fails you could try creating the tables yourself using the install.xml file in the db folder as a template.
Cheers
John