Recommending this program. It collects all your instant messagers -- AOL, MSN, Google and others -- as well as Email, Facebook and Twitter stuff, onto one bar.
I loaded it last night, configured it with everything and was chatting with someone in about 20 minutes. There was also mail streaming in from GMail and my personal box. I have it running on a Vista-based system.
It's free. It was also named a CNet top 10 product for the year.