If you are using MSN, ICQ, YAHOO or Jabber, Gaim is the opensource way to go. Gaim is available for Windows and Linux.
To redirect your buddylist (blist.xml) and other config files to an other (i)folder use the following parameter:
"C:\Program Files\Gaim\gaim.exe" --config=d:\ifolder\apps\gaim
on linux gaim -c /data/ifolder/apps/gaim
