Check the services that are running on the computer. Right-click on My Computer --> Manage --> Services and look for one or more service(s) with SQL in the name. If you find something right-click on the service, select Stop and when the service has stopped right-click on it again, select Properties and in the combo select Disable. Repeat this for each service containing SQL in its name.
As a precaution I would reboot the computer after that and check again to be sure none of the services I disabled are running any more.