Hacker access to my laptop

[Mikemets]

I had a "friend" come in and restart my computer a while ago. He's a self proclaimed computer guy. I know very little about them, but I'm learning. I run a business and he's sneaky and noisy, which of course I learned after the fact. I suspect he may have done something to gain access to my computer remotely without me knowing it. I can do a lot of my work offline so I physically removed the lan card in order to disable internet access. Is it at all possible for him to gain access from some unknown other means after the removal of the lan card and of course without running a land line even though my computer may have been corrupted by him previously. I already restarted the computer after the fact as well. What's interesting is the same start up page that he set up still shows after I restarted again so I suspect he did something that is unaffected by restarting procedures. Thank you in advance for any advice.

 

[Darren]

If it's disconnected from the internet it's very unlikely he still has access. Restarting likely will have no effect on something if he installed it.

Could do a system restore to before he messed with it.

 

[Mikemets]

Is removing the lan card while also never manually plugging into the internet via a cable a sure bet to removing oneself from the internet and hacking? Are there any other unknown devices within a computer that can somehow make it accessible to others via the internet?