It depends on the EULA (End User Licence Agreement) of the version of W8.1 that you bought. You could try having a look on click here
"I paid extra to purchase both the USB recovery disk and the license"
not quite sure what you mean by that? are they Dell products? If so then your W8.1 will be a Dell OEM W8.1 and can only be used on Dell pcs.
AFAIK with OEM W8.1 the product key is embedded in the BIOS chip.
If you got a Full Retail Version of W8.1 then you would get a separate product key and can install it on any make of pc.
Others may have more info, the above is only my view.