Should I take away the computer I loaned to my 17yr old stepson?

This computer is a loner, He needs to respect you a little more and realize that its only a loner and that looking up sites is not going to look good for him. His mother should be a little more concerned about what he is doing also this is the start of what could be a child molester or worse. You should talk to his mother again and if she thinks that its alright for him to sit in front of the computer behind locked doors, then take your computer back and let her purchase him one. This is registered to you and if anythings goes wrong it will come back on you