White screen, reboot, Nvidia drivers

Hello everyone.

I currently have a serious problem that seems to be affecting my entire computer since I installed the latest driver for the NVidia GTX 660 (334.89).

First of all, let me describe my computer, built piece by piece via Grosbill:

- it is a computer dedicated mainly to image processing, sound, and gaming (hence the i7 processor)
- Gigabyte GA H77 D3h motherboard
- Nvidia Geforce GTX 660 graphics card
- Noctua NH-D14 cooler
- Corsair TX 650 (v2) power supply
- Intel i7 3770 @3.4Ghz processor (no overclocking)
- Corsair 120 Go SSD hard drive
- updated Windows 7...
- 2 x 4Go Corsair RAM (DDR3)
+ a CD drive and an old hard drive from an old computer...
+ 1 500 Go external hard drive and one of 1 To via USB 3.0

Until now, I had a major problem: my power supply was faulty, and I had it replaced by Corsair, so all good.

Except that since I installed the latest driver, the computer has been completely crashing. Explanations:
- randomly, the screen would turn off then turn back on. Also, a white screen would appear randomly (during gaming, surfing, etc.). To me, all of this seemed like a driver issue. I contacted Nvidia support via chat, who advised me to install an older driver. Done. Same bug. Then, a new problem: the computer started to restart for no reason, without warnings, nothing.

- I then saw a rather tricky tutorial on YouTube that involved tinkering with the registry to -basically- restrict the use of Nvidia's Powermizer (power saver?): no difference, or very little, the computer eventually crashed again

- since acquiring the tower, I occasionally experienced random blue screens ("memory_management" among others)... well... self-built computer + being a non-expert = I chalked it up to coincidence... but just in case:
> I ran a Memtest to check my RAM sticks: after 1 hour (1 pass), 0 issues found. As a precaution, I left it running overnight: upon my return, the computer was off (bug? after a certain number of passes, does the computer turn off? storm?)

- I have updated all my drivers, the motherboard via @Bios, the sound card, the USB 3.0 drivers, the processor... Everything is up to date (except the graphics card, which I was advised to downgrade).

- I ran TuneUp Disk Doctor, defragmentations here and there, registry defragmentation, CCleaner, checked the whole computer with Avast!... still nothing, nothing, nothing!

- yesterday, the computer crashed twice while gaming (white screen the first time, then blue -not the BSOD, a blue like graphical bug). While gaming, I also had HWMonitor open to check the temperatures of the GPU and the CPU... but overall, the stats weren't serious: the CPU reached a maximum of 55°C while gaming;

- I also have a graphical bug on Chrome: sometimes, when minimizing/maximizing the window, the top of the browser is hidden by large random black areas: I hover over it with the mouse, and it reveals what it was hiding... strange...

- also: Photoshop and Illustrator, once opened, have sometimes crashed for no reason when I wasn't actively using them: an error message indicated an error due to the graphics card, I believe (not sure, to be confirmed).
________________

So now, I don't know anymore. I really feel like I've done my best to find a solution. I also checked the Windows error messages due to my unexpected restarts. Here are the last two:
The last one:
Log name: System
Source: Microsoft-Windows-Kernel-Power
Date: 10/03/2014 17:06:37
Event ID: 41
Task category: (63)
Level: Critical
Keywords: (2)
User: System
Computer: Leviathan
Description:
The system has restarted without shutting down properly beforehand. This error can occur if the system becomes unresponsive, has frozen, or has lost power unexpectedly.
Event XML:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Microsoft-Windows-Kernel-Power" Guid="{331C3B3A-2005-44C2-AC5E-77220C37D6B4}" />
<EventID>41</EventID>
<Version>2</Version>
<Level>1</Level>
<Task>63</Task>
<Opcode>0</Opcode>
<Keywords>0x8000000000000002</Keywords>
<TimeCreated SystemTime="2014-03-10T16:06:37.348412000Z" />
<EventRecordID>179838</EventRecordID>
<Correlation />
<Execution ProcessID="4" ThreadID="8" />
<Channel>System</Channel>
<Computer>Leviathan</Computer>
<Security UserID="S-1-5-18" />
</System>
<EventData>
<Data Name="BugcheckCode">278</Data>
<Data Name="BugcheckParameter1">0xfffffa8009f5a4e0</Data>
<Data Name="BugcheckParameter2">0xfffff88008983694</Data>
<Data Name="BugcheckParameter3">0xffffffffc000009a</Data>
<Data Name="BugcheckParameter4">0x4</Data>
<Data Name="SleepInProgress">false</Data>
<Data Name="PowerButtonTimestamp">0</Data>
</EventData>
</Event>

Before that:
Log name: System
Source: Microsoft-Windows-Kernel-Power
Date: 09/03/2014 23:08:27
Event ID: 41
Task category: (63)
Level: Critical
Keywords: (2)
User: System
Computer: Leviathan
Description:
The system has restarted without shutting down properly beforehand. This error can occur if the system becomes unresponsive, has frozen, or has lost power unexpectedly.
Event XML:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Microsoft-Windows-Kernel-Power" Guid="{331C3B3A-2005-44C2-AC5E-77220C37D6B4}" />
<EventID>41</EventID>
<Version>2</Version>
<Level>1</Level>
<Task>63</Task>
<Opcode>0</Opcode>
<Keywords>0x8000000000000002</Keywords>
<TimeCreated SystemTime="2014-03-09T22:08:27.038009700Z" />
<EventRecordID>178882</EventRecordID>
<Correlation />
<Execution ProcessID="4" ThreadID="8" />
<Channel>System</Channel>
<Computer>Leviathan</Computer>
<Security UserID="S-1-5-18" />
</System>
<EventData>
<Data Name="BugcheckCode">278</Data>
<Data Name="BugcheckParameter1">0xfffffa80084a3190</Data>
<Data Name="BugcheckParameter2">0xfffff8800fa6d0dc</Data>
<Data Name="BugcheckParameter3">0xffffffffc000009a</Data>
<Data Name="BugcheckParameter4">0x4</Data>
<Data Name="SleepInProgress">false</Data>
<Data Name="PowerButtonTimestamp">0</Data>
</EventData>
</Event>

_____________________

Note that the 2 Bug Check Codes are different... so 2 different reasons for crashing?

I hope you can help me, I'm really afraid of giving up and having to go bank with a professional or even the manufacturers if it turns out to be a hardware problem.

Thank you in advance!