You could find the relay box AKA the power distrubution center or PDC under the hood. It will have more fuses in there also, and you should double check to see if there is another fuse for the Power Windows in there too... But yeah switch the relay with another relay such as the horn relay or starter relay or AC relay... keep track of the relays as you do this in case it is bad. Somethimes you could tap them (lightly) and they will work again, but it could be an indication of it going bad... cheaper and easier to just replace it and not worry bout it again..
That 15 amp fuse was just your 12v cigarette plug in, nothing to do with the windows....