Browsing to volumio.local does not always work, especially on Windows. Check in your router which IP address was assigned to the Pi, and try to reach it by entering that address in the browser directly.
It should still work on an R-Pi 1b, but do not expect much in terms of performance. The webUI will be very slow to respond, especially if you would install additional plugins like Spotify. But give it a go, and if you like Volumio you can upgrade to a newer board