Does these components work well together?

[Reqful]

Hi

A few years ago I build the following system:

CPU: Intel® Core i7-2600K Processor
GPU: NVIDIA GeForce GTX 560 Ti
MOBO: GIGABYTE GA-P67A-UD7-B3 LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX Intel Motherboard
RAM: Corsair Dominator 12GB (6x2GB) DDR3 1600 MHz (PC3 12800) Desktop Memory (CMD12GX3M6A1600C8)
PSU: Corsair, 850w
Case: Antec Lanboy air
Operating system: Windows 7 ULTIMATE

This was my first build, so I didn't have alot of experience on computers at the time. For example, I bought 6x2 GB RAM, and my motherboard only has 4 RAM slots. (Genius!)

The problem however is that I don't think the computer is working as well as it should. Do you guys know if there is any of these components that do not work well together?
For example Grand Theft Auto IV spike laggs like crazy, and after a while my computer crashes. Same thing with Battlefield 3, it seems like the PC simply cant run it. And i have the latest update to my GPU, and everything on the software seems to be alright.

Also: I have lost some of the thumbscrews to my Antec Lanboy case. Does anyone know where I can buy a set of these screws online?

Thanks alot of any help!

 

[AMD Radeon]

they will work perfectly
put 4x2Gb ram on them and it will be decent

most people here will go for 8GB instead of 16GB as it will be a deminishing return

have you OCed the cpu? you need to unleash its potential by adding 212 EVO
your mobo does support OC as well

and please check your task manager while gaming.... maybe there are programs/virus/malware taxing you cpu/memory so you have a little room for game resources

and... putting an SSD will be very nice performance boost