Help I’m out of ideas

ok i have a compaq nc6000 laptop
the problem is that on boot up it goes straight to a flashing curser in the top left corner and stays there it gives no errors and no beeps
in cmos i can see it detects everything fine it boots from cd with no problem but this is the 3rd hard drive i replace and the 5th time i have reinstalled windows using 3 different windows cd’s
it does not boot it shows the compaq splash screen gives me the option to go into setup then goes straight into to blank screen with the curser flashing in top left corner
i would apreciate any ideas when i reload windows it works fine for a few days then it does it again

help