Hi, i'm fixing a compaq presario. i got it for free of a friend. when i got it it wouldn't turn. on. now naturally, i thought it was something to do with the ram, so i changed it. now, when i plug in the power cord, i can hear a high pitched whining noise. when i turn it on, all i see is a black screen and hear a beeep-beeeep noise from the computer. help please?