You can download and run both messengers with no problems. I've had both those as well as AIM. But might I suggest, if you're going to be using both messengers frequently, that you look into a messenger called Pidgin: http://www.pidgin.com/
It's an All in One messenger which allows you to use AIM/Yahoo/MSN all together without the need to download them all.
Is it ok to download Yahoo Messenger when I already have MSN installed or can this cause problems?
Running Windows XP 2002 SP3

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