Email/MSN Messenger…

Need a lil help i think, I am networked with 2 computers with no problems with working on them however in the last year the 2nd one is slowly not working, first it was just email but you could go into yahoo messenger and retreive it now, you can’t do that, you can’t use msn messager at all, Yahoo messenger doesn’t work, and you can load up the Yahoo home pgae but can’t access yahoo mail or Msn mail. any suggestions? Aim seems to be the only Chat thingy that works, any suggestions are welcomed.