I am using Windows 7 and JDK 6.
I downloaded the package of Android SDK with Eclipse and followed the instructions to create the first Hello World application.
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This worked for me:
simply go to device manager in your laptop or pc -> go to processes -> click on adb and -> click on end process.
Now go to sdk folder (it may be locate various location in your drive) and right click on adb.exe and click run as administrator.
Now check if it works fine.