They are simply too many! All of them store their information in different places, and a forensic investigator should know all those places: Registry, AppData folders, Program Files, Documents and Settings (which may be spelled in another language) and so on.

The problem with IMs investigation now becomes obvious. In Wikipedia you can find many more IM clients, compared here.

A few other widely used Instant Messengers are Miranda, QIP, SIM, MySpace IM, Digsby, Google Hello, Trillian, Jabber, Meebo. I am talking about the QQ messenger which is extremely popular in China and has a total of over a billion user accounts. The most interesting thing, however, is that there is a messenger which is hardly known by the average users, but has the largest audience in the world. For example, ICQ is very popular in Germany and Russia, while AIM is used mostly in the United States. However, the most preferred instant messenger varies from country to country. If you ask the average computer user (well, we all know that average people do not exist), he or she is likely to give you a list like this: AIM, Skype, Yahoo! Messenger, ICQ, MSN (now known as Live Messenger).

Icq messenger wont leave fullscreen