Note: If you installed the gtalk client in the default folder, then its more easier to make this feature enabled.Right Click on the Desktop
Paste this into the text box “c:\program files\google\google talk\googletalk.exe” /nomutex
Click Next, and name it whatever: Gtalk Multiple Login, etc.
Click OK until you are done.
Note: Don’t forget to Remove the .exe in the name (if your display file extension mode is off)
So enjoy chat with different Gmail accounts.