Read this about Versions [View:www.dummies.com/.../the-different-versions-of-windows-8.html:550:0]

[View:www.microsoft.com/.../default.aspx:550:0] 

More version Info  [View:www.microsoftstore.com/.../categoryID.62684800:550:0]

Thanks for your replies and explaining what OM means. The links had some useful information. Seems the The OEM or Retail license document explains the 4 categories

Dell support have informed me that OEM, FULL and RETAIL are the same product. I'm still not 100% sure of that though.

If your objective is a clean install, its best to download and prepare a Windows 8.1 .iso as Dell's recovery USB may have preinstalled software i.e. not lead to a "clean install".

Yes, and I had some message the other day about the Dell backup/recovery having the index missing or corrupt. So, a fresh install is needed now.

Microsoft, have recently revised their Windows 8.1 media deployment. Presuming you don't have "Windows 8.1 with Bing" edition you should have no problem assuming you pick the correct .iso http://dellwindowsreinstallationguide.com/download-microsoft-windows-and-office/download-microsoft-windows/download-windows-8-1-retail-and-oem-iso/ I would advise, booting from a Windows 8.1 USB to check whether or not you get asked for the product key. If you do (the wrong .iso), if you don't (the correct .iso).

I have followed the notes from the url, and there seems to be no method to indicate which ISO to download. Options are:

Windows 8.1
Windows 8.1 N
Windows 8.1 Pro
Windows 8.1 Pro N
Windows 8.1 Single Language

and as you say, only way to check is to see if it asks for the product key. I did talk to Microsoft chat about the options. They told me to call Microsoft, and they informed me the ISO download is only for "Retail". I'm on limited bandwidt (8 Gb/mth), so don't have the resources to download numerous ISO's. (Not even the resources to download the first one, lol )

I have used the tools mentioned on this site and obtained the OEM product key.

Once you are sure you have the correct .iso then you can safely proceed with the secure wipe using DBAN. I have no idea what "OM" stands for. A guess would be "Original Media" or "Original Manufacturer". Theres no point purchasing a full Windows 8.1 Retail license to replace a Windows 8.1 OEM license.

Even though I was hoping for a Retail or Full version of win 8.1 from Dell, I had ordered it anyway, and Dell told me it was OEM. It should arrive in a day or so. Considering the bandwidth limitations, best for now to use the win 8.1 DVD from Dell.

Thanks for your help.

From the second post in this thread, I learned about the "colour changing ink". Now I know for sure this laptop is Windows 8: magenta to green

That does not distinguish between:

Windows 8.1
Windows 8.1 N
Windows 8.1 Single Language

If you have a working install and can check system properties then you should be able to check the Windows Edition.

You can also install with the Dell media and check the Windows edition in system properties after.

You have the NON PRO aka Home version of windows 8.1

Download and save an ISO and then use an 8 gig or larger usb flash to make a bootable.

http://windows.microsoft.com/en-US/windows-8/create-reset-refresh-media

This method works with 8 or 8 Pro but you must use a generic key if you upgraded from 8.0 to 8.1 in order to install.

XHQ8N-C3MCJ-RQXB6-WCHYG-C9WKB (Win 8.1 Pro)
 
334NH-RXG76-64THK-C7CKG-D3VPT (Win 8.1 Home)

My version as you can see below is PRO

Windows 8 keys are encrypted stored in the Bios installed at the factory.  There are no more COA Stickers due to piracy. (OEM System Builder Versions Do Still have COA Stickers)

Windows 8 now comes with a Genuine Microsoft Label there are NO MORE Certificate of Authenticity (COA) Labels.

See the following examples of labels to look for.

Color-Shifting Ink
The color shift on the label is designed to change from one color to another when viewed from different angles,

making it easy to determine if it is genuine.

Windows 8: magenta to green

Windows 8 Pro: blue to purple

Windows RT: turquoise to purple

Genuine Microsoft Labels

You could try Belarc Advisor.

I don't know if this shows the key or not. (Versions Higher than 8.3c do Show the Key)

Version 8.4 supports Windows 8.1

• Operating Systems: Runs on Windows 8.1, 2012 R2, 8, 2012, 7, 2008 R2, Vista, 2008, 2003, XP, 2000, NT 4, Me, 98, and 95. Both 32-bit and 64-bit Windows are supported.
• Browsers: Runs on Internet Explorer, Firefox, Safari, Opera, and many others.

However as you change versions by adding softpacks you should save the previous keys as they are removed and replaced with the PRO and MCE packs.  But windows will not clean install with an update pack so you need the original key in order to Install clean then do windows anytime upgrades back to PRO or MCE editions.

www.belarc.com/free_download.html

You have the NON PRO aka Home version of windows 8.1

Okay thanks. So just to double check..out of the options to create the media ..

Windows 8.1
Windows 8.1 N
Windows 8.1 Pro
Windows 8.1 Pro N
Windows 8.1 Single Language

I select ..

Windows 8.1

Under the system properties, it just says Windows 8.1