Microsoft Windows XP [Version 5.1.2600] (C) Copyright 1986-2001 Microsoft Corp. C:\WINDOWS>netsh interface ipv6 delete route ?
Usage: delete route [prefix=]/[interface=][[nexthop=]][[store=]active|persistent]
prefix - Prefix of route to delete.
interface - Interface name or index.
nexthop - Gateway address, if prefix is not on-link.
store - One of the following values:
active: Deletion only lasts until next boot.
persistent: Deletion is persistent (default).
Remarks: Deletes an IPv6 route.
delete route 3ffe::/16 "Internet" fe80::1