When i try to access. when i try to access my computer it keeps saying my vista home basic is not

Question

when i try to access my computer it keeps saying my vista home basic is not genuine and leaves me with no options other than use my com with few options and put a new key in when i try a key it wont work and when i use the other option i cant access internet as i use netgear and i take it out at night so it restarts when plugged in and i have no start menue or anything