I have a 14 month year old boy and a computer. 

Unfortunately they need to share the same room sometimes.  He loves the computer and is always pressing buttons on the different parts.  I know that he knows No, and so I warn him, then if he keeps doing it I put him in his enclosed playpen, which he hates.  Once he cries a little I bring him back out and explain to him not to touch please.

Can, at this age, I expect him to understand the idea(i.e. Am I being unfair to him)?

I understand he will always test the limits and explore independence.  I still do and I'm 40!

Thanks!