You can't directly upgrade 32 bit systems to 64 bit systems. Why do this anyway? Is it for larger file accesses?
All you could do is backup all your files and then install the 64 bit system instead.
I have a major issue here. I have been trying to figured this out myself but I cant go any further.
My motherboard is a GA-P35-DS3L and I have been trying to upgrade windows 8.1 32bit to windows 8.1 64bit. I have a working usb bootable device that I tried on another computer and the usb is definitely working fine.
I tried all the boot priority options there was and even tried AHCI. Whats happening when I try to boot with the usb is I see the windows 8 logging screen logo(without the little circle below that shows its loading)... and it sits there for like 3 minutes and then the computer restart itself in an infinite loop. So since I couldn't install windows 8.1 64bit with the usb on my GA-P35-DS3L, I used another old motherboard to do it and it installed correctly and it also booted without any problems. When I put the GA-P35-DS3L back in the case and tried to load windows it shows the windows 8 loading screen logo for 3 to 6 sec and then computer restarts(right before it restarts I can see a very quick black screen with some writings at the top left corner which I cant read because its goes away too fast). Again I have tried all boot priority and also AHCI without any success. I have another Hard drive so I repeated the process on the other one and it does the same thing. Both Hard drives are working fine as I tested them both on another motherboard. My CPU is Intel core 2 duo E8600 and is 64 bit compatible.
Every other components in the PC are tested and working fine.
I tried resetting bios but its not changing anything.
I reinstalled the 32 bit version on one of the Hard drive and Its working.
Can anyone please help me find a solution for this?

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