To prevent someone from logging on with your account follow these three guidelines:

- Don't share your password with anyone.

- Don't write your password down somewhere where someone else can read it.

- Change your password regularly.

Also note you can restrict a user account to log on only specific computer in Active Directory(AD). You can also grant or deny users and group log on permissions in the computer's security policy, which can be distibuted from AD using a Group Policy Object(GPO).