Check the keyboard layout. It would be set to other region from english-US my assumption would be english-UK (British)
You are right - it is the UK keyboard. Apparently if you download the UK English iso, that is the only keyboard you get for the command prompt, and if you have a US keyboard, you're dead meat, as the '\' key is not to be found.
1. Next time, download the correct language. 2. During setup you get the keyboard, language etcetc choicesto select from.
On the UK keyboard, which has the ISO physical layout, the \ key is on the key next to the left shift which is absent on the ugly ANSI keyboards. But you should be able to get it using the usual ALT+92 combination (on the numpad)
I'm from India. I prefer UK English as opposed to American English. The keyboard, however, is the standard US type. I suppose I could download the US iso and change the language to UK English after installation.
I'm in Italy, usually I install the US versions for simplicity, then I install the italian LP, and I set the UK extended keyboard layout (because it is a perfect blend for my needs: 105 Keys ISO layout, coding characters like #{}@~ are easy to find like on US keyboard, but the accented characters like È ô à Ü are easy to find as well) Anyway I don't have your additional complication given most of the European keyboards have the ISO layout, so any European logical layout will fully fit on them.