the only way you can personally remove votes, would be to start over with that image. if the voting means that much to you to have or not have your own votes or whatever...you can save the iamge unless you have a copy located off of CMoN already, delete the gallry image, and upload it again.
this will mean any comments and votes will be lsot, as wel as the image will have a new ID number when it is activated again.
also the URL to the old image will be lost so any webpages that may contain a link to an image located on CMoN will no longer function.
for future you could find a ruler and rack his knuckles the next time he goes towards your computer so he doesn\'t do it again, or just log out of sites you don\'t want him poking around in...lol
as for the IP logging, it may be good for people that are logged in to maintain their cookie or some such, but not everyone has a static IP so i would hope that the system works with that when recording votes. rather than worrying about an IP of a registered member, just worrying that a registered member has voted. and for unregistered members it would do no good for those with dynamic IPs as they could constantly change IPs and vote forever until they ran out of IPs if IPs were used for the only way to track unregistered voting.
it is probably possible for an admin to remove your own votes from your own gallery images. but that would be at their descretion.