well you can use pidgin, which is all three combined and you can have multiple accounts of each mesenger on at once, or you can right click the shortcut, go to properties, and add a -m at the end of the target.
example-- "C:\Program Files\Ventrilo\Ventrilo.exe" -m
note the space, you do need it or it wont work. but the -m works with any program taht wont let you run multiple instances of