For word processing open office org is teh pwnage, I use it on windows even (though its definately for linux also).

You really don't need to worry about any of the things you mentioned in your post, there are many IM clients as are there media players (I especially like mplayer) but xmms is good for your music.

I expect all of these programs will be on the default mandrake install anyway, along with many others you may or may not need.