Windows 7 boots to an unresponsive black screen with mouse cursor...

Started up the PC one day and it booted to a black screen. I didn't change the configuration in any way, it just happened suddenly.

What it does:

The PC turns on like normal. I get the bios screen. I get the Windows logo screen. Then I get a black screen with a mouse cursor in the middle.

I can move the mouse, but the buttons don't do anything--left or right click.  No keys on the keyboard change the screen. Ctrl+Alt+Del does nothing. Windows key does nothing. Esc does nothing, etc. At this point the only option is to hold down the power button and turn it off.

What I've tried:

I tried to start it in safe mode, but the same thing happens. It shows the system files that are loading. The last file it shows loading is Windows/system32/DRIVERS/AtiPcie.sys then it goes to a black screen with a mouse cursor again; only this time it is in safe mode resolution so the mouse cursor is larger and not as sharp. Also, no keyboard strokes have any affect just as with normal mode.

It is a Dell Inspiron, so it came with an onboard repair utility. I used the Startup Repair tool, but it found no problems. The diagnostics tools found no issues with the hard drive or any of the other major system components. However, this error came up which appears to be related to the multi-card (SD, micro SD, etc.) reader on the front of the PC:

error code 4400:011A

msg:SCSI_1-000 DISK_generic-_SD/MMC - target not ready

It seems that this is unrelated to the black screen. I unplugged the card reader and still had the same problem. Otherwise, it passes all other tests the onboard diagnostic utility has including, memory tests, fan tests, hard drive tests, etc.

I have not, however, tried a full system restore yet. From what I've read in several forums, many have tried this in similar situations and still had the same problem. Since there are several files I'd rather not lose, I wanted to explore all other avenues.

Sorry if this is a repeat question in the forum. Most of the other situations seemed similar, but there was always something they could do that I could not, like press Ctrl+Alt+Del or boot into safe mode or whatever.

Here is as much of the system info that I can gather without having the PC on (not mine, I'm doing this for a friend):

-Dell Inspiron (I think it's a 570)

-OS: Windows 7 Home

-AMD Athlon II X2

-Integrated Video Card (I tried both the VGA output and the HDMI, which he normally uses, and both give the same results) ATI Radeon HD 4200

I hope I've been thorough enough to allow you to help me without wasting any of your time, and I thank you in advance.