Well , the initial Screenshot tool in Windows Phone did not work in Windows Phone Mango , here comes a new version of the Screenshot App for Windows Phone that works like a charm in the Mango version .
This Screenshot tool from the WPXAP Forum and allows you to take the on device screenshots easily .
I already tried this App on my Developer Unlocked Windows Phone ( HTC Mozart 7 ) and the app looks great .
Note that you require the Developer Unlocked Device to install the XAP file in your Windows Phone Device .
To install the ScreenShot App for Windows Phone , just copy the XAP file with the Application Deployment tool that comes with the Windows Phone Developer SDK and deploy it .
Once installed , follow the steps provided in this blog post from WindowsPhoneHacker.com
You are ready to use a Screenshot Tool for Windows Phone Mango .
You can download the Screenshot App fro Windows Phone Mango and how to use it from the WindowsPhoneHackerSite
Source : WindowsPhoneRocks.com