Wont connect to internet

Had to re-install windows xp on my mrs PC and now it wont connect to internet or my home network and the graphics are some sort of 1980's blockiness now,looks horrid! Havent changed any hardware inside and worked fine before re-installing xp. Had same problem last year but a mate sorted it out for me just after xmas and wish I'd paid more attention when he done it,think it was to do with network adapter drivers. Have tried everything I can think of,any technological geniuses out there know how to fix this?