i have a hp502n which i gave to my sis because she had some win95 cpu. well anyways for like 2 years ive been goin thro one problem thts a pain in the a$$. sometimes when i turn on the cpu the Hp screen comes up then it goes to a black screen with a white blinkin thing in the upper left hand corner. now its not the power suppy cause i changed it. i also do not think its the Hd cause its the second hd i had in it and its done it with both of them.. now if i kick the side of it, and restart it, it usually works. does any1 kno wht could be the prob?