there are two main options
www.trillian.ccwww.miranda-im.orgTrillian is definitely the flashier choice, which might be a drag if you aren't into constant tweaking. Miranda has its own perks—it’s lightweight and doesn't even require an installation—but those are just minor details.
By the way, you can kill off Messenger and turn off autoplay by typing gpedit.msc into start > Run.