Lenovo W150HN.Purchased on 2011 .
Windows 7 64 bit up to date.
8GB RAM , Crucial C300 SSD.
On board sound. NVIDIA 540M graphics card.
Comodo Internet Security, regularly scanned with Malwarebytes,Spybot S&D,Kaspersky Virus Cleaner.
I have a Windows CD.

Problem started happening 2 weeks AGO and I do not recall INSTALLING anything prior to that.I leave the laptop on all night to run a small program on background.I lower the resolution and put it in power saver mode with CPU throttle and sleep disabled.The program I run is not CPU/RAM/GPU intensive.Very small program that I've been using for a long time.
The problem is , the computer crashes and reboots itself overnight.When I go to Device Manager I can't find the NVIDIA graphics card and only Intel integrated one is listed.When I right click on DESKTOP, I do not see the NVIDIA control panel.If I try to reinstall the driver it says no compatible hardware is detected.
If I reboot the problem still exists,the card is not recognized.If I shut down the computer then start it, then NVIDIA comes back and everything works normal.I can even play a GPU intensive game without any hiccups.The card disappears and causes computer to reboot overnight when I leave it on.The GPu temps are not that high, around 60C.Has always been like that.The computer has been cleaned from dust internally about 5 months ago.
The Reliability Monitor shows this "Shut down unexpectedly" error
Code: [Select]BCCode: f4
BCP1: 0000000000000003
BCP2: FFFFFA8008A6E770
BCP3: FFFFFA8008A6EA50
BCP4: FFFFF800031CF7B0
OS Version: 6_1_7601
Service PACK: 1_0
Product: 256_1
the following error was from 2 days ago
Code: [Select]BCCode: 7a
BCP1: 0000000000000020
BCP2: FFFFFFFFC000009D
BCP3: FFFFFA8007805078
BCP4: 0000000000000000
OS Version: 6_1_7601
Service Pack: 1_0
Product: 256_1
This error was from March 21.It is titled "Video Hardware Error" and the details are
Code: [Select]BCCode: 117
BCP1: FFFFFA800873C320
BCP2: FFFFF880040F1D10
BCP3: 0000000000000000
BCP4: 0000000000000000
OS Version: 6_1_7601
Service Pack: 1_0
Product: 256_1

It's pretty obvious that NVIDIA is causing this problem but could this be a software related issue?I don't recall updating anything prior to that.I just ran a 2-pass Memtest86+ and RAM came up clean.Sfc /scannow came up clean as well.Computer is clean from viruses.Verified by 5 different scanners.Any ideas ? Thanks.

Edit: I installed the latest NVIDIA drivers from official website but the problem still happens.I was able to reproduce the problem.
This happens only when I throttle the CPU to less than 50% from Power Options advanced settings.Keeping it like that for few hours apparently causes a CONFLICT between NVIDIA graphics card and 2nd gen Intel i7.The problem can be considered solved.