crewcab

i have just changed my harddrive and done a reinstall i now have 2 problems 1st is i have no sound 2nd is windows xp wont reconise its a true copy i have the disk and serial code it wont reconise i have now used the code from an old computer i scrapped and it runs but gives me 30 days to registar hoew can i get sound i tried to download driver detective and it wont it says there is a fault re download i tried and get same mwssage my mother board is asrock 775i65g well thats whats printed on it i put a 300 mb sata harddrive what have i done wrond please help i know nothing about computers i usualy get a 15 yr old kid from nearby to help

as usual ive got computer problems mine now frezzes when im online and i get message page not responding it then cuts off sometimes it will start ok other times i gwt blue screen saying to chech for hardware or software issues and uninstall it ive changed nothing i was told it could be the prosser overheating if so what can i change it to i might as well get somthing better than i alresdy have i have a asrock 775 motherboard a 2,80mhz prosser ive seen several cheap on ebay 3,00 and even 4,00 will these help or even fit i know nothing about computers all this info is written on the case i got it from a neighbours son who was off to collage and needed cash help please im on xp pro