I am using a system through Remote Desktop. How can I see if any other user had logged onto the system at the same time. Also how can I check the logs as to when did someone last signed in and using what ip.
Task Manager has a Users tab which displays which users are currently logged onto the machine, whether they are currently connected, and allows you to message or remote control their sessions (given appropriate permissions).
Depending on the auditing and security policies of the current system, you can see logon events in the Event Viewer Security log. TechNet has an article that shows how to track these logon events.