I built a desktop about a month ago, and got a Sapphire HD 7870 Overclocked Edition. When it works, it works great - no graphical issues whatsoever.
However, whenever I shut down my computer and start it up again for a new session, it freezes at Windows Startup. It hangs until I'm forced to hit the hard reset button on the front of the desktop, after which the BIOS gives me the option to either proceed to Windows 7, or do Startup Repair (recommended). After this, it either proceeds (and usually fails) to repair anything, or prompts me to do a System Restore, which also usually fails to produce any permanent results. When Startup Repair fails, it gives me one of two error codes: 0x1f (can't remember what the description is), and 0x490 (System Files Integrity Check and Repair failed). After this, I am forced to shut down / restart the computer. At this point, it loads Windows 7 perfectly. However, this entire process takes from 15-45 minutes, depending how many times I have to go through Startup Repair, because it doesn't always allow me to proceed to the desktop after failing repairs.
I have isolated this issue to the graphics card (or the drivers). I've considered whether this could be a hardware issue, some kind of defect, but like I said, it works great once loaded - games play perfectly, very rare driver crashes, etc. I've experimented with taking it out of the desktop, and when I use the integrated graphics, there are never any issues - the moment I insert the card and use it as the main graphics renderer, it hangs on Windows Startup. I've looked up solutions to the error codes, but suggestions are too generic to be useful - I've tried FixMbr, registry cleans, reinstalling drivers, all that. I've attempted to install earlier drivers, but the AMD website makes it incredibly difficult to find older drivers.
I'd appreciate any pointers - at this point my solution is to never turn off my desktop until I can figure this thing out.