Windows 7 gives theme creators the ability to change the pointers used by the mouse. If you want to use Windows 7 themes but you don't like people messing with your mouse pointer, you can configure your computer to use themes without allowing the mouse pointers to be changed.

You do this by right-click on an empty area of the Desktop and selecting Personalize.

In the left panel, choose Change mouse pointers, this will open the Mouse Properties window.

In the Mouse Properties window, choose the Pointers tab.

Uncheck the box next to Allow themes to change mouse pointers and then click the Apply and OK buttons to save this change.

With this change made, you'll be able to use Windows 7 themes while maintaining the use of your original mouse pointers.