AMD driver crashes continually - Sapphire radeon HD 6670 to blame?

I built a light gaming computer around February, mainly to play Skyrim on. It was working fantastically up until about April. Now, every few minutes the screen will momentarily go black, then a notification box pops up saying "display driver stopped responding and has successfully recovered". Occasionally, the whole display just stops and the sounds go on repeat, and even ctrl + alt + delete won't get my screen back. I really hate having to shut down my computer manually. I've worked my way down the troubleshooting list on the AMD support website, to no avail. I've done the complete reinstall of windows, again with no results. I currently have no graphics driver installed, and the machine is running fine (apart from the fact that the graphics are hideous and I can't play any of my games). I've tried uninstalling old versions of the driver, running driver sweepers in safe mode, reinstalling new versions, disabling and uninstalling display adaptors in device manager, manually removing and replacing the video card to make sure the contacts are good... I'm really at a loss.

Here's my specific build:

Windows 7 64-bit

HITACHI HDS721050CLA362 (0F10381) 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

COOLER MASTER eXtreme Power Plus RS500-PCARD3-US 500W ATX12V v2.3 Power Supply

ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner

ASRock A770DE+ AM3/AM2+/AM2 AMD 770 ATX AMD Motherboard

SAPPHIRE 100323L Radeon HD 6670 1GB DDR3 PCI Express 2.1 x16 HDCP Ready Video Card

AMD Phenom II X4 970 Black Edition Deneb 3.0GHz Socket AM3 125W Quad-Core Desktop Processor

2x2 GB DDR2 RAM (originally ordered DDR3 by accident, traded with a local tech guy for another set. Could this be what's causing my issues? The set was pre-used, if gently)

I think it's the graphics card that's flaked out on me. I'm getting a little desperate. If you know of any solutions, or have any ideas, I would be eternally grateful. Or, if you know how to navigate the warrantee section of the sapphiretech website, that would be great too. I'd love to get a replacement, or my money back.

Thanks for your time.