The only Windows one I've seen to date is FirstSpot by PatronSoft but its damn expensive. The best (and cheapest) solutions generally run on dedicated hardware; even an old PC lying around could run the above software. Administration is generally web-based so you can still administer the software from a Windows machine.
I know that RouterOS allows for hotspot login pages to be very easily customised via FTP. I haven't used PublicIP myself so can't comment there.
I forgot to mention that
m0n0wall has recently added a captive portal feature and this also works very well.