Regular freeze screens

Hello,

I've been having a recurring problem with my computer for a while now. It started a couple of months ago, I'd get freeze screens about four times a week. Sometimes it would go a day or two without any problems, and then freeze the next day again. there is nothing that seems to trigger it: it can happen while gaming, while using the internet...

First thing I tried was formatting the computer. That didn't solve the problem, so I thought it would be a problem with the hardware. I brought it to the repair shop, and they didn't find any problem with the hardware. They updated my bios and told me that would solve the problem. It did, for a couple of weeks, but now it starts again! I don't know what to do anymore...

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz, Intel64 Family 6 Model 58 Stepping 9
Processor Count: 8
RAM: 16315 Mb
Graphics Card: NVIDIA GeForce GTX 770, -2048 Mb
Hard Drives: C: Total - 244095 MB, Free - 145005 MB; D: Total - 1907726 MB, Free - 1674921 MB; G: Total - 476937 MB, Free - 128150 MB;
Motherboard: ASUSTeK COMPUTER INC., P8B75-V
Antivirus: Microsoft Security Essentials, Updated and Enabled

Any help would be greatly appreciated!