help.....cursor jumping all over the place

Hi, dont know if im posting in the right place so dont shout at me if i'm not



my cursor jumps everywhere when i use my ac adaptor its okay with the battery. after about 10mins of the adaptor being plugged in it starts going daft, as soon as i pull the connection its fine but my computer only lasts about 20mins now on battery. can someone help plz



gillxxxx