they use spyware and adaware to check your cookies and temperary internet files in order to find this information out. It ends up slowing down your computer and spamming your email.

I have a patch on my msn that removes all the advertisements on my msn. it also has other benifits such as allowing me to nudge someone as many times as i wish in seconds mwahhahaha
i havent yet updated my msn to the new one tho.