ok i will run memtest86+ tonight and post the results tomorrow. i tried to update the drivers
from the device manager in control panel and all of them are up to date.
this problem occured after i gave my pc to a shop to fix it from another problem. the story is that after i arrived from the summer holidays to my town, my pc was on but my screen was black and didn't receive any sign from the pc. so i sent it to a shop to fix it, and they told me that the motherboard was insterted wrong in pc, although my pc was working right for 3 years, and they changed the way it was placed so that it would be ok. well i took it back and when i tried to use it the same thing happened. my pc was open but there was no sign on the screen. So i send it to another shop where he told me that something was wrong with the BIOS and that he had to reset them and then my pc was working again. but since then 2 usb ports on the side of the tower are not working and i am having these random freezes..