Error while enabling a core module
You somehow have aggregator uninstalled with its tables existing, which should not be. By examining aggregator_schema() in aggregator.install you can see that upon installation aggregator will create several tables named aggregator_(something). Table names correspond to the keys of the array returned by aggregator_schema(). If any of those tables exist you must delete them from the database before attempting to enable the aggregator module. As always, back up and understand how to restore your database first before attempting something like this and rehearse on a test system.