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If you are using the default aero theme I can change that for you. Using Windows Style Builder.
If you are using a custom theme you will need to ask the theme maker. It's not cool to change someone else work.
This will be making a custom theme so you will need to do 1 of these 2 ways of Enabling custom themes for it to work. Enabling Custom Themes - Windows 7
Or Theme - How to Apply Custom Themes
All I need from you would be a name to call the custom theme and I can post it here for you. Let me know if you would like me to do it.
Here is a screenshot of it.