Windows 8.1 32bit to Windows 10 64bit

Hi all, this is my first post here

I've updated 2 machines from 7 64 bit and 8.1 64 bit to Windows 10 64 bit ok.

However... I have a Dell Inspiron 530 from 2007 which originally came with Vista Home 32 bit.

I took advantage of the cheap Vista > 8 upgrade a few years ago (£25?) and then the free 8 > 8.1 upgrade.

So... currently this machine is running 8.1 32 bit. I've read that a product key is valid for both 32 and 64 bit Windows.
If this is the case, once I successfully upgrade to Windows 10 32 bit, will I be able to extract the product key and re-install 10 64 bit from scratch and re-input the extracted key?

The only reason I want to do this is to increase the RAM on this old machine.

I would like to know this as well. I have already upgraded all of my machines, but I found that several of them were running 32-bit Windows 7. I used the 32-bit media creation tool just to make sure there were no compatibility issues. If I decide in the future to do a clean install of windows 10, I would like to be able to use Windows 10 64-bit.

will I be able to extract the product key and re-install 10 64 bit from scratch and re-input the extracted key?

If you are clean installing the 64 bit version of Windows 10 over the activated legal
upgrade version of the 32 bit version of Windows 10 you don't need a key at all.

Luckily for you that crappy Pentium Dual-Core E2160 is a 64 bit CPU!

I realise I need to clean install to go 32>64

What I'm asking is whether I cam extract the product key from a 32 bit install then clean install 64 bit with that key.

The machine is currently running 8.1 32bit. I've got the reserved icon and that's still pending, however...

I tried using the 32 bit media creation tool and doing an in-place upgrade. It was going through the motions until an error along the lines of "Windows cannot change the reserved space" (or some-such). Then rolled itself back to 8.1

I then tried a 64 bit install from USB - when asked for product key I input the key I extracted with Belarc but was rejected as not valid.

The original key on the machine's sticker is for 32 bit Vista. I paid for the upgrade to 8 with media centre (no longer have the email confirmation). Then the free 8.1 update through the store.

You do realize you will lose access to Media Center if you upgrade to Windows 10, right?

What I'm asking is whether I cam extract the product key from a 32 bit install then clean install 64 bit with that key.

You don't need ANY key!