Deleting or reinstalling applications
Deleting an application removes it from your phone and clears some memory space. It also removes any information that the application contained. So you should remove them with care.
To delete apps
On Start, flick left to the Application list.
Press and hold an application, then press Uninstall.
When asked for confirmation, press Yes.
To delete games
On Start, press Games.
In Collection, press and hold a game, then press Uninstall.
Xbox LIVE and Marketplace may not be available in your country or region.
If you accidentally delete an application, or ever have to replace your phone, you can reinstall applications or games that you've bought without paying for them again (as long as they're still in Marketplace).
You won't be able to reinstall an application unless you have Windows Phone 7.5. If you're not sure which software version is currently installed on your phone or how to install an update, visit Update central.
To reinstall apps from your phone
On Start, press Marketplace .
Press Search to find the application or game that you want to reinstall.
If it's a free application or game, press Install. Otherwise, press Buy. On the confirmation screen, you'll see a message saying you've already purchased this application. Press Install to install it again.
Follow the instructions to reinstall the application. You might have to re-enter your Windows Live ID.
The Windows Phone Store on the web also provides a detailed purchase history, in case you've forgotten what you've bought. Phone applications and games sync directly with your phone and are not part of your media collection in the Zune software (or Windows Phone 7 Connector for Mac) on your computer.