Re: No true privacy?
It depends on what your ISP decides to keep on file; they're required by law to at least keep something on you in case law enforcement needs to view or monitor your internet activity in a criminal investigation, but for that they would need a warrant.
But, given how much people use computers these days, it's impossible for an ISP to log every single thing you do; and even then, they only keep the records for so long (unless they're Google. Google saves users' searches for 40 years).
As for this MSN thing you're talking about...chat and email/messaging sites usually keep detailed logs of conversations, just in case. I heard Facebook never erases profiles from their system.
Just don't worry about it, though. Unless you've shown up on America's Most Wanted, chances are nobody's that interested.
If you're worried about your hard drive, just break it or something.