Remove extensions on Chrome that appear by default

I installed something, but the installer had an option to install an extra item with it. Even though I thought I told it not to, it did it.

This extra item I installed put an extension into Chrome. I can go and un-install the extension, but if I create a new user within Chrome, it appears there again, and even worse, if someone logs into the new user, it syncs that persons extensions locally, and the extra extension doesn't disappear.

Later, Chrome realizes it has this extra extension, but it isn't synced online, so it goes ahead and does this, so now this user has this extension from my computer on his personal computer.

I couldn't find this program in the un-install area in the control panel, or the programs folder.

I would really like to get rid of it. I'm guessing the extension is added to some folder within chrome, so I would be able to manually go to that directory and manually delete it.

I went through some programs and uninstalled some that I didn't recognize and knew they weren't there last time I looked at that page. after that the problem disappeared, so it must of been part of another program or was under a different name. I still would like to know how a program like that puts its extension into Chrome in case this problem ever happens again however, but I can't currently test any answers posted