Hi Ray!
There are a many ways to get back to the IM window but three that quickly come to mind are:
1 - click on the 'Send Instant Message' link on the left side of a forum thread under a member's name;
2 - click on a member's name to get their member profile to display and then click on the 'Send Instant Message' link to the right of the member's name; or
3 - go to the 'Who's Online' page and click on the link on the far right hand side under the heading 'IMsg'.
In the IM window once the 'To Messages' and/or 'From Messages' links are clicked the messages are deleted from both your and the receiver's IM queue if they have been read by both.
Hope that helps a little.
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Jim Olson
"The Toys"...!!! Save the Wave!
Where I've been in a Corvette...!!!