Saga Lout
OK, that was a good one. On the off chance that the OP is interested in finding the ISP as his/her school, library, or whatever, I suggest
ipconfig/all
Note the DNS server. Then do a "whois " on the DNS server IP address. It's not always correct, but sometimes...
EDIT: or download a traceroute tool and ping Google. At least one of the nodes along the route will belong to the ISP.