Windows 7 is stuck at “Starting Windows” when I attempt to boot computer

Basically, whenever I turn on my computer, it gets to the Starting Windows phase and just stays there. The startup animation still plays, yet it gets nowhere.

• I have tried booting into safe mode, however it gets stuck at loading CLASSPNP.SYS. It then freezes there and doesn't continue booting.

• I have tried booting into recovery mode from the hard drive, and it freezes after displaying the background image. I have tried booting from a recovery CD, which works, and I was able to use system restore. However, using system restore did not fix it, and it still is stuck at the Starting Windows screen.

• I have tried booting a Windows CD (Windows 8 Retail Installer) to see if I could upgrade it to fix this issue, however that froze at a blank screen after it got past the boot logo.

• I have tried changing around the BIOS settings (including resetting), to no avail.

• I have tried re-plugging the internal PSU cables (this is a custom-built desktop), yet this has changed nothing.

• I can boot into a loopback Ubuntu install on the same drive, which works fine, other than the fact that it has issues with some of the USB ports and the network card.

• This system has worked fine for the past few months, completely stable, and nothing in the configuration has changed before this error started happening.

• Startup Repair on the Windows recovery CD doesn't find any issues.

• Unplugging my secondary hard drive or swapping around memory doesn't change anything.

• The hard drive itself is fine, it hasn't shown any signs of failure and once again, boots my other OS fine.

If anyone could help with this, that would be great. I can't seem to find any possible solution to this.

If it makes any difference, my system specs are as follows:

• AMD FX-8320
• Gigabyte GA-970A-D3
• 4GB of DDR3
• Radeon HD 6870
• 550w PSU

I'd like to not have to reinstall Windows, for I have more than a terabyte of data that I would have to back up if that becomes the only option.

EDIT: I have since tried the following:

• Tried the solution involving restoring files from RegBackup, which changed nothing.

• Tried testing everything with Hiren's boot CD, everything comes back as fine.

• Tried disabling everything unnecessary in the BIOS and unplugging everything unneeded, it still hangs.

• Tried swapping out every possible combination of RAM, it still has the same result. The RAM is not at fault it seems

• Tried every GPU I own (which is many!) and it still hangs at the exact same place.

• Tried minimizing the power consumption as much as possible, even using an old PCI graphics card. It still hangs at the same place in the same way, signifying that it's not the PSU at fault.

• Tried resetting the BIOS again, still nothing.

• Tried every possible combination of BIOS options, even downclocking everything, it still hangs in the same spot.

• Tried upgrading the BIOS from version FB to FD, which changed nothing.

Based on this, I would conclude the motherboard to be at fault. Are there any other possibilities? I don't want to spend $150 for a new motherboard.

EDIT 2: This is what it gets stuck at when I try to boot into safe mode:

Note the slight graphical corruption at the top of the screen. No matter how I set up the system, this seems to be there. In addition, either it has stopped booting into safe mode now, or it takes upwards of 2+ hours, and I haven't left it running for that long.