Windows 7: Pinned Taskbar item open new icon instead of on top of pinned item?

I've got two laptops here. Both running Windows 7. On one when you pin an item to the taskbar and run that program it does not open another icon on the taskbar.

On this one it will open a new icon on the taskbar.



Why is this the case and how do I fix it please?

is it firefox that is duplicating the icon?

Yes it is Firefox. Thanks

Pin the new instance of FireFox and unpin the old one,then drag the new one where you choose ,
The reason for it happening is because of the last update you made .
After you have unpinned the old one it won't open two instances again , until next update ,though it didn't happen to me with ff 10

to me it always happens with itunes, i just unpin the old one and pin the new one.
but this time it happened with google chrome, and that method doesn't work anymore

any suggestions?

it really bugs me, there should be solution,no?

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