you need to make sure taht the seperate option is ticked so that they extract as a new object and there is an option somewhere to 'keep faces together' which needs to be selected.
In Maya 8 it's at the top of the edit mesh menu but that won't help you much as you're on Maya 7. If memory serves me correctly, under either the 'polygon' menu there is an option for tools. Open that menu and the 'keep faces together' option should be there.
It's a while since I used Maya 7 so I could be miles off about where the option is but i's definately what you're after.