Having again some access to the important computer is not the same as actually having the computer.
Your next task should be discovering the computer's location,
so that you could go there and collect it.
But how to do it?
You think you could insert some program
which will survive on the computer undiscovered until today
then it will activate and upload the computer's location somewhere.
But how can the program discover the computer's location in space?
And how can you be sure that the computer still exists, still works and is or will be turned on?
Or maybe you should leave a message to whoever finds the computer
and promise a big reward for returning it to you?
Or maybe something else?
This will require some thinking.