64 bit - Can I upgrade from Windows 7 32bit to 64bit without formatting?

My friend installed Windows 7 on his computer (upgrading from XP).

He wasn't sure if his processor supported x64 or not, so he installed the x86 version, just to be on the safe side.

After I looked it up, it turns out his processor does support x64, and now we want to upgrade.

The question is: is it possible to upgrade without completely re-installing the OS?

Can I? Or do I have to format the C: partition again?

Answer

No. x86/32-bit to x64/64 bit is not supported in any version of Windows.

See also: Upgrade from Windows 7 32 bit to 64 bit

Tip for your friend:

1. Almost any CPU sold in the last decade is 64 bit capable.


2. You can look it up on the web, but briefly
   If it is an AMD it will be 64bit capable (those have been that way for ages).
   If it is an Intel check on http://ark.intel.com/


3. He could just have tried the 64 bit version of Windows 7. Worst case it would fail during the installation.