I found out that my PC is 64 bit after getting help from here:
https://social.technet.microsoft.com/Forums/windows/en-US/16cc73c7-31ec-47d4-a198-62cd3fc65e42/my-computer-shows-two-different-type-of-processor-at-different-points-which-is-the-right-one-should?forum=w8itproinstall
I want to know if I will be able to use the same key when I do a clean installation for windows 8.1 pro 64 bit?
also i'm doing this to use my 4gb ram (already installed on my computer), am i correct to do this or should i stick to the 32 bit version? 

No it will not. It's a different OS technically, so your 32-bit key will only work with Windows 8.1 Pro x86 version. 

but it says here that it will:
https://social.technet.microsoft.com/Forums/windows/en-US/05f1754a-d0da-4189-81ce-121fdba2ddb6/is-this-possible-to-reinstall-the-window-8-pro-64-bit-on-window-8-pro-32-bit-with-the-same-product?forum=w8itproperf

so which is it? Im confused 

Hi,   Am 14.07.2015 19:50, schrieb WatchOutforShredder: > I want to know if I will be able to use the *same* key when I do a > clean installation for windows 8.1 pro 64 bit?   In all my MSDN downloads, it is the same Key. There is no difference in 32 or 64 Bit regarding to the key.   I know some OEM Vendors, that only ship a product key thats fits a 32 or 64Bit Version of Windows. Depending on what you baught.   So, in the end it is not a general answered question, it is depending on your Version you baught. Take a look in your EULA or ask your OEM   If you got both install DVDs 32/64bit, than it´s the same key :-)   Mark -- Mark Heitbrink - MVP Windows Server - Group Policy   Homepage: http://www.gruppenrichtlinien.de - deutsch GPO Tool: http://www.reg2xml.com - Registry Export File Converter  

• Proposed as answer by Tripredacus 17 hours 30 minutes ago

I upgraded from XP-32bit to Windows 8.1 pro (I bought online )
Thanks for the help! Ill delete my key from this one ( 32 bit version ) and start do a clean installation of the 64-bit  version then.

Hi,   Am 14.07.2015 19:50, schrieb WatchOutforShredder: > I want to know if I will be able to use the *same* key when I do a > clean installation for windows 8.1 pro 64 bit?   In all my MSDN downloads, it is the same Key. There is no difference in 32 or 64 Bit regarding to the key.   I know some OEM Vendors, that only ship a product key thats fits a 32 or 64Bit Version of Windows. Depending on what you baught.   So, in the end it is not a general answered question, it is depending on your Version you baught. Take a look in your EULA or ask your OEM   If you got both install DVDs 32/64bit, than it´s the same key :-)   Mark -- Mark Heitbrink - MVP Windows Server - Group Policy   Homepage: http://www.gruppenrichtlinien.de - deutsch GPO Tool: http://www.reg2xml.com - Registry Export File Converter  

• Proposed as answer by Tripredacus Wednesday, July 15, 2015 1:53 PM
• Marked as answer by WatchOutforShredder 22 hours 43 minutes ago

Yes, you should be able to use the same product key for both the 32 bit and 64 bit Windows 8.1. 
Also take a look at License key valid for both. Although it references Windows 7, it also applies to Windows 8.1. 
If you do not have your Windows 8.1 media you may be able to use the page Upgrade Windows with only a product key.
When changing between architecture, you must always perform a full, clean installation. You should make sure that all of your data, pictures, music, or anything that you want to keep, are backed up.