There is no failover builtin into windows routing, but I have seen people using scripts to monitor an interface and if the interface doesnt replies change its metric or delete the route from windows so all traffic goes to the second route.
I haven't got that script on me (as I have never had the need to use it) but it is accomplished via vbs script
http://www.google.co.uk/search?hl=en&ei=0vgMS63eCeOj4gbUusTxBw&sa=X&oi=spell&resnum=0&ct=result&cd=1&ved=0CAgQBSgA&q=windows+routing+failover+vb+script&spell=1
http://www.experts-exchange.com/Networking/Misc/Q_20940521.html