Winpcap should have an add/remove program entry. What you do depends on if you use it or not. Do you use a packet sniffer (eg. Wireshark) or something like that?
As for removing Winpcap without the add/remove entry, it would probably be easiest to reinstall it again to get the add/remove entry back. Removing it manually would be fairly awkward.
edit: OK.. moving it now.