my problem is that when i push the button to start my pc, i only see in the monitor rectangles that change colors. the full screen looks like that.never happen to mi before. no idea what happen.
First off disconnect HDD power cable. Afterwards, clean RAM stick/s for any corrosion. Then test one by one if you have more than one stick. If that doesn't works remove CMOS battery for five minutes. Put it back again and test. If that doesn't help then likely you have a either a bad RAM module or video card.
What about RAM modules? If you need assistance on how to use an soft eraser to clean them, Google is your friend. Even in video you can find help.