I Agree... All the networking needs testing, try moving the pc to another socket that you know works ! You shouldn't need to go as far as reloading the pc... maybe a repair to correct any damaged drivers and service packs. What is you current network? 10/100, wireless, etc.... You said you have tried another card, was it the same make? and definatly good? It seems a little odd tho... can you think of anything that may have caused it? i.e. lighting etc?