Once I turn in my hp I get a blue screen!!!!!

Hello,
I bought my Hp about 2-3 yrs ago, i sent it back before the warranty expired-- and the mother board was replaced. The problem was that once i turn off the hp then i turn on the screen turns blue and is preparing to crash dump...Its runs as if the computer is repairing but it does not... this always happens so i never turn it off. i also hear a sound- which i was told is the needle scratching an indicating the hard drive is giving out... Besides the battery is fried. I can never keep my comp unplugged..What is your recommendation. do i need a hard drive and if soo what is the model i should buy?? Thanks Mari.
Oh another problem is that i can not uninstall a program now to install a new one...