Alternative downloaded Instant Messenger software: is that you need a multi-protocol instant messaging application (Yahoo, MSN, AIM-AOL, ICQ, Jabber) ALL-IN-ONE package you will need one of those downloaded files below:

For MAC: Adium, Fire, iChat and Proteus

For Windows: Digsby, Miranda IM, Trillian

For Linux/Unix-like: Kopete

For multi-platform: Pidgin and SIM

What is multiprotocol instant messaging application? (wiki)
http://en.wikipedia.org/wiki/Multiprotocol_instant_messaging_application

Use google.com or download.com or filehippo.com to obtain one of mentioned name of multi-protocol IM software depend on which OS platform you are use.

For Linux OS, use either Application/Add and Remove Software or Synaptic Package Manager to obtain .deb package for mentioned software to be installed for you.