I had a problem with my laptop a few years back which resulted in it having to be completely wiped and windows reloaded. Since then I've had problems with some hardware and drivers on my laptop, such as my built in wireless, my webcam and most recently, my graphics card. It is a NVIDIA Geforce 8400, but is only showing 64mb of graphics memory when I look at my computer's specifications. I am not sure how much it was before the wipe, but it was certainly more than that. Since my laptop is a few years old, Sony Vaio does not supply new drivers or any support on their website for my model of laptop.
Any advice would be appreciated, will give more information if needed!
Make sure you have all of the available Windows updates installed if possible.You never know if any of them can fix the issues your having.But if all of those things are failing then I would think the problem is due to overheating.