Windows 7 Home hangs at “Welcome” screen

UPDATE 3: I'm currently assisting him in getting a spare hard drive ready to migrate data over to a new Windows 7 installation. On top of that I'm having him run Windows Memory Diagnostic, then will have him run a few passes of memtest86+ to see if anything is wrong memory-wise. The freezing seems to be happening at extremely random times. I'm also going to run a Malware/virus check on his computer, but since he hardly downloads programs and generally practices safe browsing habits I doubt it's that. I may run Prime95 and some sort of GPU Benchmark test to make sure it's not the CPU/GPU either.

UPDATE 2.1: Ran CrystalDiskInfo for SMART data info. C5 Current Sector Pending Count is 84. C6 Uncorrectable sector count is 83. Should I be worried?

UPDATE 2: It looks like his profile got corrupted, so I made a new profile and copied over the settings. It seemed OK for a little while. However, a few hours later, his explorer.exe ended up freezing AGAIN after he tried accessing the System Properties window. Then he got this error:

"The instruction at 0x776F5319 referenced memory at 0x71CE84E4.the required data was not placed into memory because of an I/O error status of 0xc000000e.
Click on ok to terminate the program."

Then the computer reset itself – it froze at the FOXCONN logo – after another restart the computer booted up again fine.

Something tells me the hard drive is going bad. What do you all think?

UPDATE: chkdsk /R allowed him to boot back to the Windows 7 desktop, but his desktop profile got completely reset. I'm trying to remote into his machine now to see if he's logged on as a temporary profile so I'll post an update soon.

ORIGINAL QUESTION BELOW

I'm asking on behalf of a friend who's currently having problems with his machine. Windows 7 Home 32-bit. He's too far away for me to help by going over to his house – I'm helping him over the Internet.

This is his current machine: http://www.newegg.com/Product/Product.aspx?Item=N82E16883227134

The only two changes he made to that machine is to swap out the gfx card for a EVGA GTX 460 and the PSU for a Corsair TX650.

Here's what happened:
He was playing a computer game (fairly CPU/GPU intensive) and had some music going in the background in foobar while playing. Suddenly, he notices the music stopped playing, so he switches to foobar to try to close it, but it freezes up (window won't respond). So he figures it's just foobar having a bad day and force quits that program. Suddenly, his game won't respond, so he force quits that, then the entire computer just went to crap at that point, so he hits the restart button on his machine.

Computer POSTS fine, but now he gets stuck at the Windows "welcome" screen (his account is set to auto-login). HD activity light is solid yellow but he doesn't hear HDD activity. He tried booting into Safe Mode – gets stuck at the "welcome screen". Tried a STartup Repair within Windows 7, it found a few problems, but still gets stuck at welcome. I advised him to boot off the DVD – sfc /scannow found nothing (couldn't use the regular /scannow option; says there's a repair pending, had to use use offbootdir/offwindir command switches). Ran startup repair 3 times – found nothing.

My friend runs virus/malware scans on a regular basis, so he's fairly sure it's not that either.

Right now I'm having my friend run chkdsk /R on the computer while in this Startup Recovery mode – so far it's caught a few bad sectors.

However at this point I'm kinda wondering which way to go if chkdsk doesn't fix it. Quick Google search said someone had success by booting Windows with bootlogging on – some others have success with running the aforemented chkdsk, etc. The fact that Windows cannot even boot into Safe Mode concerns me.

While we're waiting for chkdsk /R to finish, are there any other options I can give my friend short of reinstalling Windows 7? He has his data on a separate partition so that's not a major problem (though it'll be an annoyance for him). I suspect his hard drive may be having some issues, but my main concern is getting him back up and running before we start diagnosing the hard drive (I may have him run some sort of SMART test utility later).