Is the windows 8 upgrade 32 bit or 64bit
Currently I installed Windows 8 Pro 32-bit. Is it possible to upgrade Windows 8 32-bit to 64-bit one? During installation I don't see any option to choose between 32-bit and 64-bit.
No, because of the computer architecture. Those two setups are set on installation (how the CPU will treat the data, will it use 32-bit buses or 64-bit buses, addresses, etc.) and cannot be simply 'upgraded'.
You would need to reinstall the OS, as said above. In average system usage, there isn't much difference though.
Wikipedia has a good article on pros and cons - 64-bit vs 32-bit and describes the differences.
I don't think so, but I found on the web this link...