Do u have more than 1 gmail id and want to login to google chat engine at a time with all ur Gmail id's.

Install Google talk, right click the Google talk desktop icon->Properties->Short Cut tab->Target->Append at the end with the following string with out any quotation.
" /startmenu /nomutex"

Note: there is a space before first forward slash as well as second forward slash.

Click Ok button

Now double click on the google Talk icon as many times as u want and login with your different Google id's.

Happy Chatting :-)