How to upgrade to 64-bit windows 8.1?

[Lagulous]

I have a laptop with an x64 based processor, so it supports 64bit. But Windows 8.1 came on the laptop when I bought it, so I don't have an installation CD or any some such thing. Can I upgrade to a 64bit version of Windows 8.1?

 

[basroil]

You need to follow the instructions at http://windows.microsoft.com/en-us/windows-8/create-reset-refresh-media to make an install media and reinstall Windows. You WILL lose all installed software by doing so, and you should back up everything before attempting.