I'm not sure if this will work for V7 to CS4 (it does for CS3) and you don't say if you're on Mac or Windows, so I'll do my best to give you a generic answer that works!
If you do a search for a folder called "ModifiedWorkspaces" you'll find an xml file for your personal workspace. "Workspaces.xml" should be in the folder above where you found the previous ModifiedWorkspaces folder. It's in the preferences folder basically, but these are hidden in different places depending on the platform. So a simple search is just as simple.
Hope that helps,
Ben
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