Re-install windows 8 from windows 7

Some time ago I bought & installed windows 8. I bought online direct from microsoft. I didn't like it & used a disc image to return to windows 7.
I now wish to try windows 8.1 & need to install windows 8 to do the upgrade.
I have no record or product key for my purchase of windows 8.
Where do I go from here or am I stuffed?

Check your email from MS Store.

Looked before & couldn't find it. Looked again and there it was.
Thanks.

@ denebarry: you should be good to go! Just make sure you create bootable usb media in the process.

What do you mean? Create a bootable win8.1 USB stick after installation or win7 before or both?

Where do I redownload win8 with existing product key?

... workin on it, give me a few minutes.
I'm in the process of downloading a fresh copy right now, I'll let you know how it goes.

Go here, read everything and click on the big blue 'Install Windows 8' button; it'll save a Setup file to your downloads......

About.com: http://windows.microsoft.com/en-US/windows-8/upgrade-product-key-only

... run it;
it'll ask for your product key, if that checks out your on your way;
it will proceed to download the necessary files, (which is what I'm in the middle of), bout 15 min...

I don't need to install 8.0 before 8.1

Don't bother downloading 8.0 just use the ltlle trick to d/l 8.1 iso file.

Install it using generic key:

Then activate with your original 8.0 key.

Keys for 8.1 install:

Core=334NH-RXG76-64THK-C7CKG-D3VPT
Professional=XHQ8N-C3MCJ-RQXB6-WCHYG-C9WKB

Enter slmgr.vbs -ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX (Replace X's with your RETAIL Windows 8.0 key)

Take a look at those posts for more info.

http://www.eightforums.com/tutorials/18309-windows-8-windows-8-1-iso-download-create.html

How to download Windows 8.1 ISO with a Windows 8 key.
http://www.eightforums.com/installation-setup/33164-how-download-windows-8-1-iso.html

http://www.eightforums.com/installa...retail-windows-8-1-windows-8-product-key.html

D/l both the windowssetup.exe ( for 8.0)

AND
windowssetupbox.exe from

Upgrade Windows with only a product key - Microsoft Windows Help

Run windowssetup.exe and enter your 8.0. key When it starts to d/l, close it.

Then run windowssetupbox.exe

That will download 8.1 without asking for any other key.

Thanks everyone. I'm making Disc image of win 7 installation now. Will tackle install of 8. 1during the week.