I've been working on removing spyware from a client's computer. I have removed the majority of infestations. They are saying now that they don't want to pay for my work and they just want their machine back.

I'm OK with returning the machine to them, but I'm going to make sure there is plenty of spyware on it...just like it was when it came into the shop. (I'm not OK with them not paying, but I'm willing to write it off as a good lesson).

What is the most efficient way to install spyware on a machine, without having to go around to all of the porn sites that this user did?

Thanks,
Rhoads