boot - Windows XP x64 hangs at welcome screen

The problem is that when I boot on Windows XP (x64), which worked very great for a great amount of time, the mouse pointer and the welcome screen appears but then after waiting hour or so nothing changes and it won't proceed to the Log On screen where I should enter my password. I have Windows 8.1 (Update 1) also installed. So here are the things I tried (without success):

Actions:

1. 
   

   Booting in all kinds of safe mode.

   
   


2. 
   

   Changing AHCI to IDE in BIOS settings.

   
   


3. 
   

   Changing primary Graphics Device from PCI-E to onboard in BIOS settings.

   
   


4. 
   

   Replacing the C:\Windows\System32\Config\SYSTEM registry with an older backed up copy.

   
   


5. 
   

   Deleting the HKLM\SYSTEM\MountedDevices registry entry.

   
   


6. 
   

   Checking the system disk for errors (No errors were found).

   
   

Result of them:

Nothing changes - Windows XP still boots up successfully but hangs on this screen:

I have totally lost hope what the problem can be. If it was some bugged start-up services then swapping the registry with an very absolute copy of them would fix the problem, right? Otherwise - you see the problem is not in the drive as when I checked it - no errors were found. Also I have changed a lot of BIOS settings with no result as well. And lastly I've also tried to replace WinLogon.exe with Explorer.exe but then the system refuses to launch it and automatically restarts. I have also tried testing an early MessageBoxW call, before the WinLogon.exe WinMain function but with the same result stated above - the system crashed.

I'm also trying to debug WinLogon.exe to see the problem in real-time but unfortunately I have a lot of bad time with this as it seems it can't be done locally so I need either to buy an USB debug cable for a lot of money or an PCI-E Firewire card. But I should maybe create a different question for this topic.