Lazy Web Request – Way to have 2 people signed into IM on same PC under same login

If I were to put out a ‘family pc’ or ‘family mac’ (have to be polically correct about PC) and wanted both my wife and I to be able to hear IM buzzes if they happened, is there a way to be signed in on one user login, and have two IM clients going?

For example, have AIM, Y! and MSN logged in  for person A, and GAIM logged in for person B? Will the protocols conflict?