See Administrators and Remote Users
Determine which administrators and remote users have access to a Windows server.
This article applies to: Managed Servers
The easiest way to determine who has access to a particular Windows machine is to go into computer management (compmgmt.msc) and look in Local Users and Groups.
Check the Administrators group and the Remote Desktop Users group to see who belongs to these. Those people have local administrator and remote desktop user privileges respectively.
To find the computer management application, you can search for it on your machine.