Plugins on certain multisites

Hi,

I’m having a bit of a dilemma. I need a way of having a plugin enabled on some sites but not others. The reason being that a video plugin I used to use upsets the built in video embedding, but I need the videos on the older blogs to work and can’t tamper with them due to moderation.

Does anyone know of a way I can do this? Don’t want to play too much by myself as I don’t want to upset the apple cart.

Thanks