My internet does not work right

Hello,
i can log onto my internet fine, however when i try and log onto serten web sites it will only load the first page, after that i can click on amything and it eather give me a blank screen doesnt do anything or does not finish loading. I was told that its not a computer problem and that it is not a internet problem. I use dial up i get 28 kbs. I have a bran new computer that i have already reinstalled everything in it after reformating it from windows home addition service pac 3 to a servce pack 2. only half of my internet works for example yahoo does not work but gmail works fine. none of the job sights work and i had to quite college because it would not let me get ino the class room. i have tryed everything i can think of and nothing works i even had my phone company over to see if my line was ok. were the prblem occured was when my computers hard drive whent down i got it fixed and now the internet is not working and has not ever sence. what do i do